1st Year NotesChemistry class 11th

Class 11 Chemistry Important Questions

Class 11 Chemistry Important Questions On Newsongoogle By Bilal Articles

Unlock the key to success in Class 11 Chemistry with essential resources on Newsongoogle by Bilal Articles! Dive into important questions, comprehensive chapter notes, past papers, and insightful guess papers. Elevate your understanding of Chemistry with expertly curated content designed for Class 11 students. Boost your academic performance and excel in Chemistry studies with our specialized educational materials.

Important Questions for Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry.

Q1. What will be the mass of one atom of C-12 in grams?
Q2. How many significant figures should be present in answer to the following calculation?
Q3. What is the symbol for the SI unit of the mole? How is the mole defined?
Q4. What is the difference between molality and molarity?
Q5. Calculate the mass percent of calcium, phosphorus and oxygen in calcium phosphate Ca3(PO4)2
Q6. 45.4 L of dinitrogen reacted with 22.7 L of dioxygen and 45.4 L of nitrous oxide was formed. The reaction is given below:
Q7. If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in a whole-number ratio.
Is this statement true?
If yes, state according to which law?
Give one example related to this law.
Q8. Calculate the average atomic mass of hydrogen using the following data:
Q9. Hydrogen gas is prepared in the laboratory by reacting dilute HCI with granulated zinc.
Q10. The density of the 3 molal solution of NaOH is 1.110 g mL–1. Calculate the molarity of the solution.
Q11. Volume of a solution changes with change in temperature, then, will the molality solution be affected by temperature? Give reason for your answer.
Q12. If 4 g of NaOH dissolves in 36 g of H2O, calculate the mole fraction of each component in the solution. Also, determine the molarity of solution (specific gravity of solution is 1g ml-1)
Q13. The reactant which is entirely consumed in the reaction is known as a limiting reagent.

Assertion and Reason Type Questions

Q1. Assertion (A): The empirical mass of ethene is half of its molecular mass.
Reason (R): The empirical formula represents the simplest whole-number ratio of various atoms present in a compound.
(i) Both A and R are true and R is the correct explanation of A.
(ii) A is true but R is false.
(iii) A is false but R is true.
(iv) Both A and R are false.
Q2. Assertion (A): One atomic mass unit is defined as one-twelfth of the mass of one carbon-12 atom.
Q3. Assertion (A): Significant figures for 0.200 are 3 whereas for 200 it is 1.
Reason (R): Zero at the end or right of a number is significant provided they are not on the right side of the decimal point.
(1) Both A and R are true and R is the correct explanation of A.
(ii) Both A and R are true but R is not a correct explanation of A.
(iii) A is true but R is false.
(iv) Both A and R are false.

Long Questions

Q1. A vessel contains 1.6 g of dioxygen at STP (273.15K, 1 atm pressure). The gas is now transferred to another vessel at a constant temperature, where pressure becomes half of the original pressure. Calculate
(i) volume of the new vessel.
(ii) number of molecules of dioxygen.
Q2. Calcium carbonate reacts with aqueous HCl to give CaCl2 and CO2 according to the reaction given below:
CaCO3 (s) + 2HCl (aq) → CaCl2(aq) + CO2(g) + H2O(l)
Q3. A box contains some identical red coloured balls, labelled as A, each weighing 2 grams. Another box contains identical blue coloured balls, labelled as B, each weighing 5 grams. Consider the combinations AB, AB2, A2B and A2B3, and show that a law of multiple proportions is applicable.

Important Questions for Class 11 Chemistry Chapter 2 Structure of Atom.

Q1. Arrange s, p and d sub-shells of a shell in the increasing order of effective nuclear charge (Zeff) experienced by the electron present in them.
Q2. Show the distribution of electrons in an oxygen atom (atomic number 8) using an orbital diagram.
Q3. Nickel atom can lose two electrons to form Ni²+ ion. The atomic number of nickel is 28. From which orbital will nickel lose two electrons?
Q4. Which of the following orbitals are degenerate?
Q6. The arrangement of orbitals on the basis of energy is based upon their (n+l) value. Lower the value of (n+1), the lower is the energy. For orbitals having the same values of (n+l), the orbital with a lower value of n will have lower energy.
Q7. Which of the following will not show deflection from the path on passing through an electric field?
Q8. An atom having atomic mass number 13 has 7 neutrons. What is the atomic number of the atom?
Q9. Wavelengths of different radiations are given below:
Q10. The electronic configuration of the valence shell of Cu is 3d10 4s1 and not 3d9 4s2. How is this configuration explained?
Q11. According to de Broglie, the matter should exhibit dual behaviour, that is, both particle and wave like properties. However, a cricket ball of mass 100 g does not move like a wave when it is thrown by a bowler at a speed of 100 km/h. Calculate the wavelength of the ball and explain why it does not show wave nature.
Q12. What is the experimental evidence in support of the idea that electronic energies in an atom are quantized?
Q13. Out of electrons and protons which one will have a higher velocity to produce matter waves of the same wavelength? Explain it.
Q14. A hypothetical electromagnetic wave is shown in Fig. Find out the wavelength of the radiation.
Q15. What is the difference between the terms orbit and orbital?

Assertion and Reason Type Questions

Q1. Assertion (A): All isotopes of a given element show the same type of chemical behaviour. Reason (R): The chemical properties of an atom are controlled by the number of electrons in the atom.
Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
Both A and R are false.
Q2. Assertion (A): Black body is an ideal body that emits and absorbs radiation of all frequencies.
Reason (R): The frequency of radiation emitted by a body goes from a lower frequency to a higher frequency with an increase in temperature.
Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the explanation of A
A is true and R is false;
Both A and R are false.
Q3. Assertion (A): It is impossible to determine the exact position and exact momentum of an electron simultaneously.
Reason (R): The path of an electron in an atom is clearly defined.
Both A and R are true and R is the correct explanation of A.
Both A and R are true and R is not the correct explanation of A.
A is true and R is false.
Both A and R are false.

Long Questions

Q1. What is the photoelectric effect? State the result of a photoelectric effect experiment that could not be explained on the basis of laws of classical physics. Explain this effect on the basis of quantum theory of electromagnetic radiation.
Q2. When an electric discharge is passed through hydrogen gas, the hydrogen molecules dissociate to produce excited hydrogen atoms. These excited atoms emit electromagnetic radiation of discrete frequencies which can be given by the general formula.
Q3. Calculate the energy and frequency of the radiation emitted when an electron jumps from n = 3 to n = 2 in a hydrogen atom.
Q4. Why was a change in the Bohr Model of atom required? Due to which important development (s), the concept of movement of an electron in an orbit was replaced by, the concept of probability of finding an electron in an orbital? What is the name given to the changed model of the atom?

Class 11 Classification of Elements and Periodicity in Properties Important Questions with Answers

  1. Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.
  2. All transition elements are d-block elements, but all d-block elements are not transition
  3. Identify the group and valency of the element having atomic number 119. Also, predict the
    outermost electronic configuration and write the general formula of its oxide.
  4. Ionisation enthalpies of elements of second period are given below :
    Ionisation enthalpy/ kcal mol-1 : 520, 899, 801, 1086, 1402, 1314, 1681, 2080.
    Match the correct enthalpy with the elements and complete the graph given in Fig. 3.1.
    Also, write symbols of elements with their atomic number.
  5. Among the elements B, Al, C and Si,
    (i) which element has the highest first ionisation enthalpy?
    (ii) which element has the most metallic character?
    Justify your answer in each case.
  6. Write four characteristic properties of p-block elements.
  7. Choose the correct order of atomic radii of fluorine and neon (in pm) out of the options
    given below and justify your answer.
    (i) 72, 160
    (ii) 160, 160
    (iii) 72, 72
    (iv) 160, 72
  8. Illustrate by taking examples of transition elements and non-transition elements that
    oxidation states of elements are largely based on electronic configuration.
  9. Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However,
    oxygen has lower ionisation enthalpy than nitrogen. Explain.
  10. First member of each group of representative elements (i.e., s and p-block elements)
    shows anomalous behaviour. Illustrate with two examples.

Long Questions

  1. Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.
  2. Define ionisation enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.
  3. Justify the given statement with suitable examples— “the Properties of the elements are a periodic function of their atomic numbers”.
  4. Write down the outermost electronic configuration of alkali metals. How will you justify their placement in group 1 of the periodic table?
  5. Write the drawbacks in Mendeleev’s periodic table that led to its modification.

Important Questions for Class 11 Chemistry Chapter 4 – Chemical Bonding and Molecular Structure.

  1. Explain the non linear shape of H2S and non planar shape of PCl3 using valence shell electron pair repulsion theory.
  2. Using molecular orbital theory, compare the bond energy and magnetic character of O2+ and O2– species.
  3. Explain the shape of BrF5.
  4. Structures of molecules of two compounds are given below:
    (a) Which of the two compounds will have intermolecular hydrogen bonding and which compound is expected to show intramolecular hydrogen bonding.
    (b) The melting point of a compound depends on, among other things, the extent of hydrogen bonding. On this basis explain which of the above two compounds will show higher melting point.
    (c) Solubility of compounds in water depends on power to form hydrogen bonds with water. Which of the above compounds will form a hydrogen bond with water easily and be more soluble in it.
  5. Why does type of overlap given in the following figure not result in bond formation?
  6. Explain why PCl5 is trigonal bipyramidal whereas IF5 is square pyramidal.
  7. Elements X, Y and Z have 4, 5 and 7 valence electrons respectively.
  8. Draw the resonating structure of
    (i) Ozone molecule
    (ii) Nitrate ion
  9. What is meant by the term average bond enthalpy? Why is there a difference in bond enthalpy of O – H bond in ethanol (C2H-OH) and water?

Assertion and Reason Type Questions

  1. Assertion (A): Sodium chloride formed by the action of chlorine gas on sodium metal is a stable compound.
    Reason (R): This is because sodium and chloride ions acquire octet in sodium chloride formation.
    (i) A and R both are correct, and R is the correct explanation of A.
    (ii) A and R both are correct, but R is not the correct explanation of A.
    (iii) A is true but R is false.
    (iv) A and R both are false.

Long Questions

  1. i) Discuss the significance/ applications of dipole moment.
  2. Use the molecular orbital energy level diagram to show that N2 would be expected to have a triple bond, F2 a single bond and Ne2 no bond.
  3. Briefly describe the valence bond theory of covalent bond formation by taking an example of hydrogen. How can you interpret energy changes taking place in the formation of dihydrogen?
  4. Describe hybridization in the case of PCl5 and SF6. The axial bonds are longer as compared to equatorial bonds in PCl5 whereas in SF6, both axial bonds and equatorial bonds have the same bond length. Explain.
  5. (i) Discuss the concept of hybridization. What are its different types in a carbon atom?
    (ii) What is the type of hybridization of carbon atoms marked with stars?

Important Questions for Class 11 Chemistry Chapter 5 – State of Matter.

  1. If 1 gram of each of the following gases are taken at ST P, which of the gases will occupy
    (a) greatest volume and (b) smallest volume?
  2. Physical properties of ice, water and steam are very different. What is the chemical composition of water in all three states?]
  3. The behaviour of matter in different states is governed by various physical laws. According to you what are the factors that determine the state of matter?
  4. Use the information and data given below to answer the questions (a) to (c):
    o Stronger intermolecular forces result in higher boiling point.
    o Strength of London forces increases with the number of electrons in the molecule.
    o Boiling point of HF, HCI, HBr and HI are 293 K, 189 K, 206 K and 238 K respectively.
    (a) Which type of intermolecular forces are present in the molecules HF, HCI, HBr and HI?
    (b) Looking at the trend of boiling points of HCI, HBr and HI, explain out of dipole- dipole interaction and London interaction, which one is predominant here.
    (c) Why is boiling point of hydrogen fluoride highest while that of hydrogen chloride lowest?
  5. What will be the molar volume of nitrogen and argon at 273.15K and 1 atm?

Long Questions

  1. Isotherms of carbon dioxide at various temperatures are represented In Fig. 5.5. Answer the following questions based on this figure.
  2. The variation of the vapour pressure of different liquids with temperature is shown in Fig. 5.6.
  3. Why does the boundary between the liquid phase and gaseous phase disappear on heating a liquid to critical temperature in a closed vessel? In this situation what will be the state of the substance?
  4. Why does a sharp glass edge become smooth on heating it up to its melting point In a flame? Explain which property of muds is responsible for this phenomenon.
  5. Explain the term ‘laminar flow’. Is the velocity of molecules the same in all the layers in laminar flow? Explain your answer.

Important Questions for Class 11 Chemistry Chapter 6 – Chemical Thermodynamics.

  1. 18.0 g of water completely vapourises at 100°C and 1 bar pressure and the enthalpy change in the process is 40.79 kJ mol–1. What will be the enthalpy change for vapourising two moles of water under the same conditions? What is the standard enthalpy of vapourisation for water?
  2. One mole of acetone requires less heat to vapourise than 1 mol of water. Which of the two liquids has a higher enthalpy of vapourisatIon?
  3. The value of ΔfHӨ for NH3 is – 91.8 KJ mol–1. Calculate enthalpy change for the following reactIon:
  4. Given that ΔH = 0 for mixing of two gases. Explain whether the diffusion of these gases into each other in a closed container is a spontaneous process or not?
  5. Heat has a randomising influence on a system and temperature is the measure of the average chaotic motion of particles in the system. Write the mathematical relation which relates these three parameters.

Long Questions

  1. Derive the relationship between ΔH and ΔU for an ideal gas. Explain each term Involved in the equation.
  2. Extensive properties depend on the quantity of matter but intensive properties do not. Explain whether the following properties are extensive or intensive.
  3. The lattice enthalpy of an ionic compound is the enthalpy when one mole of an ionic compound present in its gaseous state, dissociates into its ions. It is impossible to determine it directly by experiment. Suggest and explain an indirect method to measure lattice enthalpy of NaCl(s).
  4. ΔG is net energy available to do useful work and is thus a measure of “free energy”. Show mathematically that ΔG is a measure of free energy. Find the unit of ΔG. If a reaction has positive enthalpy change and positive entropy change, under what condition will the reaction be spontaneous?
  5. Graphically show the total work done in an expansion when the state of an ideal gas is changed reversibly and isothermally from (pi, Vi ) to (pf, Vf ). With the help of a pV plot compare the work done in the above case with that carried out against a constant external pressure pf.

Important Questions for Class 11 Chemistry Chapter 7 – Equilibrium.

Q1. The ionisation of hydrochloric in water is given below:
Q2. The aqueous solution of sugar does not conduct electricity. However, when sodium
chloride is added to water, it conducts electricity. How will you explain this statement on
the basis of ionisation and how is it affected by the concentration of sodium chloride?
Q3. BF3 does not have protons but still acts as an acid and reacts with NH3. Why is it so? What
Q4. The ionisation constant of a weak base MOH, is given by the expression.
Q5. Conjugate acid of a weak base is always stronger. The decreasing order of basic strength of the following conjugate bases will be?
Q6. Arrange the following in increasing order of pH.
Q8. On the basis of the equation pH = – log [H+], the pH of 10-8 mol dm-3 solution of HCI
should be 8. However, it is observed to be less than 7.0. Explain the reason

Long Questions

Q1. How can you predict the following stages of a reaction by comparing the value of Kc and Qc?
(i) Net reaction proceeds in the forward direction.
(li) Net reaction proceeds in the backward direction.
(iii) No net reaction occurs.
Q2. On the basis of the Le Chatelier principle explain how temperature and pressure can be
adjusted to increase the yield of ammonia in the following reaction.
Q3. A sparingly soluble salt having general formula A P*x B9 and molar solubility S is in
equilibrium with its saturated solution. Derive a relationship between the solubility and solubility product for such salt.
Q4. Write a relation between ΔG and Q and define the meaning of each term and answer the.

Important Questions for Class 11 Chemistry Chapter 8 – Redox Reaction.

Q1. MnO42- undergoes a disproportionation reaction in an acidic medium but MnO4– does not. Give a reason.
Q2. PbO and PbO₂ react with HCl according to the following chemical equations:
Q3. Nitric acid is an oxidising agent and reacts with PbO, but it does not react with PbO₂. Explain why?
Q4. Write a balanced chemical equation for the following reactions:
Q5. Calculate the oxidation number of phosphorus in the following species.
Q6. Calculate the oxidation number of each sulphur atom in the following compounds:

Long Questions

Q1. Explain redox reactions on the basis of electron transfer. Give suitable examples.
Q2. On the basis of standard electrode potential values, suggest which of the following reactions would take place? (Consult the book for Eo value).
Q3. Why does fluorine not show a disproportionation reaction?
Q4. Find out the oxidation number of chlorine in the following compounds and arrange them in increasing order of oxidation number of chlorine.
Q5. Which method can be used to find out the strength of the reductant/oxidant in a solution? Explain with an example.

Important Questions for Class 11 Chemistry Chapter 9 – Hydrogen.

Q1. How can production of hydrogen from water gas be increased by using a water gas shift reaction?
Q2. What are metallic/interstitial hydrides? How do they differ from molecular hydrides?
Q3. Name the classes of hydrides to which H2O, B2H6, and NaH belong.
Q4. If the same mass of liquid water and a piece of ice is taken, then why is the density of ice less than that of liquid water?
Q5. Complete the following equations:
Q6. Give reasons:
(i) Lakes freeze from top towards bottom.
(ii) Ice floats on water.
Q7. What do you understand by the term ‘auto protolysis of water’? What is its significance?
Q8. Discuss briefly de-mineralisation of water by ion exchange resin.
Q9. Give reasons why hydrogen resembles alkali metals?
Q10. Hydrogen generally forms covalent compounds. Give reason.
Q11. Why does the water show a high boiling point as compared to hydrogen sulphide? Give reasons for your answer.
Q12. Why can dilute solutions of hydrogen peroxide not be concentrated by heating? How can a concentrated solution of hydrogen peroxide be obtained?
Q13. Why is hydrogen peroxide stored in wax lined bottles?
Q14. Why does hard water not form lather with soap?
Q15. Phosphoric acid is preferred over sulphuric acid in preparing hydrogen peroxide from peroxides. Why?

Long Questions

Q1. Atomic hydrogen combines with almost all elements but molecular hydrogen does not. Explain.
Q2. How can D2O be prepared from water? Mention the physical properties in which D₂O differs from H2O. Give at least three reactions of D2O showing the exchange of hydrogen with deuterium.
Q3. How will you concentrate H₂O₂? Show differences between structures of H₂O₂ and H₂O by drawing their spatial structures. Also mention three important uses of H₂O₂.
Q4. (i) Give a method for the manufacture of hydrogen peroxide and explain the reactions involved therein.
(ii) Illustrate oxidising, reducing and acidic properties of hydrogen peroxide with equations.
Q5. What mass of hydrogen peroxide will be present in 2 litres of a 5 molar solution? Calculate the mass of oxygen which will be liberated by the decomposition of 200 mL of this solution.
Q6. A colourless liquid ‘A’ contains H and O elements only. It decomposes slowly on exposure to light. It is stabilised by mixing urea to store in the presence of light.
(i) Suggest possible structure of A.
(ii) Write chemical equations for its decomposition reaction in light.
Q7. An ionic hydride of an alkali metal has significant covalent character and is almost unreactive towards oxygen and chlorine. This is used in the synthesis of other useful hydrides. Write the formula of this hydride. Write its reaction with Al2Cl6.
Q8. Sodium forms a crystalline ionic solid with dihydrogen. The solid is nonvolatile and non conducting in nature. It reacts violently with water to produce dihydrogen gas. Write the formula of this compound and its reaction with water. What will happen on electrolysis of the melt of this solid.

Important Questions for Class 11 Chemistry Chapter 10 – The s-Block Elements.

Q1. How do you account for the strong reducing power of lithium in aqueous solution?
Q2. When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li,
Q3. Complete the following reactions.
Q4. Lithium resembles magnesium in some of its properties. Mention two such properties and give reasons for this resemblance.
Q5. Name an element from Group 2 which forms an amphoteric oxide and a water soluble sulphate.
Q6. Discuss the trend of the following:
(i) Thermal stability of carbonates of Group 2 elements.
(ii) The solubility and the nature of oxides of Group 2 elements.
Q8. All compounds of alkali metals are easily soluble in water but lithium compounds are more soluble in organic solvents. Explain.
Q9. In the Solvay process, can we obtain sodium carbonate directly by treating the solution.
Q10. Write the Lewis structure of O2– ion and find out oxidation state of each oxygen atom? What is the average oxidation state of oxygen in this ion?

Long Questions

Q1. The s-block elements are characterised by their larger atomic sizes, lower ionisation enthalpies, invariable +1 oxidation state and solubilities of their oxosalts. In the light of these features describe the nature of their oxides, halides and oxosalts.
Q2. Present a comparative account of the alkali and alkaline earth metals with respect to the
following characteristics:
o (i) Tendency to form ionic / covalent compounds
o (li) Nature of oxides and their solubility in water
o (iii) Formation of oxosalts
o (iv) Solubility of oxosalts
o (v) Thermal stability of oxosalts
Q3. When a metal of group 1 was dissolved in liquid ammonia, the following observations were obtained:
(i) Blue solution was obtained initially.
Q4. The stability of peroxide and superoxide of alkali metals increase as we go down the group. Explain giving reason.
Q5. When water is added to compound (A) of calcium, solution of compound (B) is formed.
When carbon dioxide is passed into the solution, it turns milky due to the formation of
compound (C). If excess of carbon dioxide is passed into the solution milkiness disappears
due to the formation of compound (D). Identify the compounds A, B, C and D. Explain why the milkiness disappears in the last step.

Important Questions for Class 11 Chemistry Chapter 11 – The p-Block Elements.

Q1. Draw the structures of BCI3.NH3 and AlCl3 (dimer).
Q2. Explain the nature of boric acid as a Lewis acid in water.
Q3. Draw the structure of boric acid showing hydrogen bonding. Which species is present in water? What is the hybridisation of boron in this species?
Q4. Explain why the following compounds behave as Lewis acids.
(i) BCl3
(ii) AlCl3
Q5. Give reasons for the following:
(i) CCI4 is immiscible in water, whereas SiCl4 is easily hydrolysed.
(ii) Carbon has a strong tendency for catenation compared to silicon.
Q6. Explain the following :
o (i) CO2 is a gas whereas SiO2 is solid.
o (ii) Silicon forms SiF62- ion whereas the corresponding fluoro compound of carbon is not known.
Q7. The +1 oxidation state in group 13 and +2 oxidation state in group 14 becomes more and more stable with increasing atomic number. Explain.
Q8. Carbon and silicon both belong to the group 14, but inspite of the stoichiometric similarity,
the dioxides, (i.e., carbon dioxide and silicon dioxide), differ in their structures. Comment.
Q9. If a trivalent atom replaces a few silicon atoms in three-dimensional network of silicon dioxide, what would be the type of charge on the overall structure?
Q10. Aluminium dissolves in mineral acids and aqueous alkalies and thus shows amphoteric character. A piece of aluminium foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning matchstick near the mouth of the test tube, a pop sound indicates the evolution of hydrogen gas. In the same activity when performed with concentrated nitric acid, the reaction doesn’t proceed. Explain the reason.

Long Questions

Q1. Describe the general trends in the following properties of the elements in Groups 13 and 14.
(i) Atomic size
(ii) Ionisation enthalpy
(iii) Metallic character
(iv) Oxidation states
(v) Nature of halides
Q2. Account for the following observations:
Q3. When aqueous solution of borax is acidified with hydrochloric acid, a white crystalline solid is formed which is soapy to touch. Is this solid acidic or basic in nature? Explain.
Q4. Three pairs of compounds are given below. Identify that compound in each of the pairs Group 13 element is in more stable oxidation state Give reason for your choice. State the nature of bonding also.
Q5. Boron fluoride exists as BF3 but boron hydride doesn’t exist as BH3. Give reason. In which form does it exist? Explain its structure.
Q6. (i) What are silicones? State the uses of silicones.
(i) What are boranes? Give chemical equation for the preparation of diborane.
Q7. A compound (A) of boron reacts with NMe3 to give an adduct (B) which on hydrolysis gives a compound (C) and hydrogen gas. Compound (C) is an acid. Identify the compounds A, B and C. Give the reactions involved.
Q8. A nonmetallic element of group 13, used in making bullet proof vests is extremely hard solid of black colour. It can exist in many allotropic forms and has unusually high melting point. Its trifluoride acts as Lewis acid towards ammonia. The element exhibits maximum covalency of four. Identify the element and write the reaction of its trifluoride with ammonia. Explain why does the trifluoride act as a Lewis acid.
Q9. A tetravalent element forms monoxide and dioxide with oxygen. When air is passed over heated element (1273 K), producer gas is obtained. Monoxide of the element is a powerful reducing agent and reduces ferric oxide to iron. Identify the element and write formulas of its monoxide and dioxide. Write chemical equations for the formation of producer gas and reduction of ferric oxide with the monoxide.

Important Questions for Class 11 Chapter 12 – Organic Chemistry Some Basic Principles and Techniques.

Q1. Which of the above compounds form pairs of metamers?
Q2. Identify the pairs of compounds which are functional group isomers.
Q3. Identify the pairs of compounds that represents position isomerism.
Q4. Identify the pairs of compounds that represent chain isomerism.
Q5.For testing halogens in an organic compound with AgNO3 solution, sodium extract (Lassaigne’s test) is acidified with dilute HNO3. What will happen if a student acidifies the extract with dilute H2SO4 in place of dilute HNO3?
Q6. What is the hybridisation of each carbon in H2C = C = CH2?
Q7. Explain, how is the electronegativity of carbon atoms related to their state of hybridisation in an organic compound?
Q8. Show the polarisation of carbon-magnesium bonds in the following structure.
Q9. Compounds with same molecular formula but differing in their structures are said to be structural isomers. What type of structural isomerism is shown by.
Q10, Which of the following selected chains is correct to name the given compound according to the IUPAC system.
Q11. In DNA and RNA, nitrogen atoms are present in the ring system. Can Kjeldahl method be used for the estimation of nitrogen present in these? Give reasons.
Q12. If a liquid compound decomposes at its boiling point, which method (s) can you choose for its purification. It is known that the compound is stable at low pressure, steam volatile and insoluble in water.

Long Questions

Q1. What is meant by hybridisation? Compound CH2 = C = CH2 contains sp or sp2 hybridised carbon atoms. Will it be a planar molecule?
Q2. Benzoic acid is an organic compound. Its crude sample can be purified by crystallisation from hot water. What characteristic differences in the properties of benzoic acid and the impurity make this process of purification suitable?
Q3. Two liquids (A) and (B) can be separated by the method of fractional distillation. The boiling point of a liquid (A) is less than the boiling point of a liquid (B). Which of the liquids do you expect to come out first in the distillate? Explain.
Q4. You have a mixture of three liquids A, B and C. There is a large difference in the boiling points of A and the rest of the two liquids i.e., B and C. Boiling points of liquids B and C are quite close. Liquid A boils at a higher temperature than B and C and the boiling point of B is lower than C. How will you separate the components of the mixture. Draw a diagram showing the setup of the apparatus for the process.
Q5. Draw a diagram of a bubble plate type fractionating column. When do we require such type of a column for separating two liquids? Explain the principle involved in the separation of components of a mixture of liquids by using a fractionating column. What industrial applications does this process have?
Q6. A liquid with a high boiling point decomposes on simple distillation but it can be steam distilled for its purification. Explain how is it possible?

Important Questions for Class 11 Chapter 13 – Hydrocarbons.

Q1. Why do alkenes prefer to undergo electrophilic addition reaction while arenes prefer electrophilic substitution reactions? Explain.
Q2. Alkynes on reduction with sodium in liquid ammonia form trans alkenes. Will the butene thus formed on reduction of the 2-butyne show the geometrical isomerism?
Q3. Rotation around the carbon-carbon single bond of ethane is not completely free. Justify the statement.
Q4. Draw Newman and Sawhorse projections for the eclipsed and staggered conformations of ethane. Which of these conformations is more stable and why?
Q5. The intermediate carbocation formed in the reaction of HI, HBr and HCl with propene is the same, and the bond energy of HCl, HBr and HI are 430.5 kJmol−1, 363.7 kJmol−1 and 296.8 kJmol−1, respectively. What will be the order of reactivity of these halogen acids?
Q6. What will be the product obtained from the following reaction, and why?
Q7. How will you convert benzene into
(i) p – nitrobromobenzene
(ii) m – nitrochlorobenzene
Q8. Arrange the following set of compounds in the order of their decreasing relative reactivity with an electrophile. Give reason.
Q9. Despite their – I effect, halogens are o- and p-directing in haloarenes. Explain.
Q10. Why does the presence of a nitro group make the benzene ring less reactive than the unsubstituted benzene ring? Explain.

Long Questions

Q1. An alkyl halide C5H11Br (A) reacts with ethanolic KOH to give an alkene ‘B’, which reacts with Br2 to give a compound ‘C’, which on dehydrobromination provides an alkyne with ‘D’. On treatment with sodium metal in liquid ammonia, one mole of ‘D’ gives one mole of the sodium salt of ‘D’ and half a mole of hydrogen gas. Complete hydrogenation of ‘D’ yields a straight-chain alkane. Identify A, B, C and D. Give the reactions involved.
Q2. 896 mL vapour of a hydrocarbon ‘A’ having carbon 87.80% and hydrogen 12.19% weighs 3.28g at STP. Hydrogenation of “A’ gives 2-methyl pentane. Also, “A’ on hydration in the presence of H2SO4 and HgSO4 provides a ketone with ‘B’ having molecular formula C6H12O. The ketone ‘B’ gives a positive iodoform test. Find the structure of “A’ and give the reactions involved.
Q3. An unsaturated hydrocarbon “A’ adds two molecules of H2 and on reductive ozonolysis gives butane-1,4-di-al, ethanal and propanone. Give the structure of ‘A’, write its IUPAC name and explain the reactions involved.
Q4. In the presence of peroxide addition of HBr to propene takes place according to anti-markovnikov’s rule but the peroxide effect is not seen in the case of HCI and HI. Explain.

Important Questions for Class 11 Chapter 14 – Environmental Chemistry.

Q1. Greenhouse effect leads to global warming. Which substances are responsible for greenhouse effect?
Q2. Acid rain is known to contain some acids. Name these acids and where do they come from in rain?
Q3. Ozone is a toxic gas and is a strong oxidising agent even then its presence in the stratosphere is very important. Explain what would happen if ozone from this region is completely removed?
Q4. Dissolved oxygen in water is very important for aquatic life. What processes are responsible for the reduction of dissolved oxygen in water?
Q5. On the basis of chemical reactions involved, explain how de chlorofluorocarbons cause thinning of the ozone layer in the stratosphere.
Q6. What could be the harmful effects of improper management of industrial and domestic solid waste in a city?
Q7. During an educational trip, a botany student saw a beautiful lake in a village. She collected many plants from that area. She noticed that villagers were washing clothes around the lake and at some places waste material from houses was destroying its beauty. After a few years, she visited the same lake again. She was surprised to find that the lake was covered with algae, stinking smell was coming out and its water had become unusable.Can you explain the reason for this condition of the lake?
Q8. What are biodegradable and non-biodegradable pollutants?
Q9. What are the sources of dissolved oxygen in water?
Q10. What is the importance of measuring the BOD of a water body?
Q11. Why does water covered with excessive algal growth become polluted?
Q12. A factory was started near a village. Suddenly villagers started feeling the presence of irritating vapours in the village and cases of headache, chest pain, cough, dryness of throat and breathing problems increased. Villagers blamed the emissions from the chimney of the factory for such problems. Explain what could have happened. Give chemical reactions for the support of your explanation.
Q13. Oxidation of sulphur dioxide into sulphur trioxide in the absence of a catalyst is a slow process but this oxidation occurs easily in the atmosphere. Explain how does this happen. Give chemical reactions for the conversion of SO₂ into SO3.
Q15. How is ozone produced in stratosphere?

Long Questions

Q1. How can you apply green chemistry for the following:
(i) to control photochemical smog.
(ii) to avoid the use of halogenated solvents in drycleaning and that of chlorine in bleaching.
(iii) to reduce the use of synthetic detergents.
(iv) to reduce the consumption of petrol and diesel.
Q2. Green plants use carbon dioxide for photosynthesis and return oxygen to the atmosphere, even then carbon dioxide is considered to be responsible for greenhouse effect. Explain why?
Q3. Explain how does greenhouse effect cause global warming.
Q4. A farmer was using pesticides on his farm. He used the produce of his farm as food for rearing fishes. He was told that fishes were not fit for human consumption because large amount of pesticides had accumulated in the tissues of fishes. Explain how did this happen?
Q5. For dry cleaning, in the place of tetrachloroethane, liquefied carbon dioxide with suitable detergent is an alternative solvent. What type of harm to the environment will be prevented by stopping use of tetrachloroethane? Will use of liquefied carbon dioxide with detergent be completely safe from the point of view of pollution? Explain.

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