Sample Paper

Question 1. The pressure volume work for an ideal gas can be calculated by using the expression;

$w = - \int_{V_i}^{V_f} p_{ex} dV$

The work can also be calculated from the pV plot by using the area under the curve within the specified limit. When an ideal gas is compressed reversibly or irreversibly from volume $V_i$ to $V_f$, which of the following is correct?

(i) $w_{rev} = w_{irrev}$

(ii) $w_{rev} < w_{irrev}$

(iii) $w_{rev} > w_{irrev}$

(iv) $w_{rev} = w_{irrev} + p_{ex} \cdot dV$

Question 2. When hydrochloric acid is added to cobalt nitrate solution at room temperature, the following reaction takes place :

$[Co(H_2O)_6]^{3+}(aq) + 4Cl^-(aq) \rightleftharpoons [CoCl_4]^{2-}(aq) + 6H_2O(l)$

(Pink) (Blue)

The solution is blue at room temperature. However, it turns pink when cooled in a freezing mixture. Based upon this information, which of the following expression is correct for the forward reaction?

(i) $\Delta H > 0$

(ii) $\Delta H < 0$

(iii) $\Delta H = 0$

(iv) The sign of $\Delta H$ cannot be predicted on the basis of this information.

Question 3. Which of the following elements does not form hydride by direct heating with dihydrogen?

(i) Be

(ii) Mg

(iii) Sr

(iv) Ba

Question 4. Which of the following species should be aromatic in character?

(i)

(ii)

(iii)

(iv)

Question 5. Identify the pairs which are of isotopes?

(i) $^{12}_6X, ^{13}_6Y$

(ii) $^{35}_{17}X, ^{37}_{17}Y$

(iii) $^{14}_6X, ^{14}_7Y$

(iv) $^8_4X, ^8_5Y$

Question 6. Electrophiles are electron seeking species. Which of the following sets consist of electrophiles only.

(i) $BF_3, NH_3, H_2O$

(ii) $AlCl_3, SO_3, NO_2^+$

(iii) $NO_2^+, CH_3^+, CH_3-C^+=O$

(iv) $C_2H_5^-, C_2H_5^+$

Question 7. How many significant figures should be present in the answer of the following calculations?

$\frac{2.5 \times 1.25 \times 3.5}{2.01}$

Question 8. Complete the following reactions

(i) $O_2^{2–} + H_2O \rightarrow$

(ii) $O_2^– + H_2O \rightarrow$

Question 9. Give IUPAC name of the compound whose line formula is given below:

Question 10. Green house effect leads to global warming. Which substances are responsible for green house effect?

Question 11. Using molecular orbital theory, compare the bond energy and magnetic character of $O_2^+$ and $O_2^–$ species.

Question 12. Consider the reaction given below :

$CaCO_3(s) \rightarrow CaO(s) + CO_2(g)$

Predict the effect of increase in temperature on the equilibrium constant of this reaction.

Given that $\Delta_f H^\ominus[CaO(s)] = –635.1 \text{ kJ mol}^{-1}$

$\Delta_f H^\ominus[CO_2(g)] = –393.5 \text{ kJ mol}^{-1}$

$\Delta_f H^\ominus[CaCO_3(s)] = –1206.9 \text{ kJ mol}^{-1}$

Question 13. pH of $0.08 \text{ mol dm}^{–3}$ HOCl solution is 2.85. Calculate its ionization constant.

Question 14. Nitric acid is an oxidising agent and reacts with PbO but it does not react with $PbO_2$. Explain why?

Question 15. Calculate the strength of 5 volume $H_2O_2$ solution.

Question 16. According to de Broglie, matter should exhibit dual behaviour, that is both particle and wave like properties. However, a cricket ball of 100g does not move like a wave when it is thrown by a bowler at a speed of 100km/h. Calculate the wavelength of the ball and explain why it does not show wave nature.

Question 17. Explain why nitrogen has positive electron gain enthalpy whereas oxygen has negative, although first ionisation enthalpy of oxygen is lower than that of nitrogen. Justify your answer.

Question 18. Write Lewis structure of the following compounds and show formal charge on each atom.

$HNO_3, NO_2, H_2SO_4$

Question 19. Although heat is a path function, even then heat absorbed by the system under certain conditions is independent of path. What are those conditions? Explain.

Question 20. The solubility product of $Al(OH)_3$ is $2.7 \times 10^{–11}$. Calculate its solubility in g $L^{–1}$ and also find out pH of this solution. (Atomic mass of Al is 27 u).

Question 21. Calculate the oxidation number of each sulphur atom in the following compounds:

(a) $Na_2S_2O_3$

(b) $Na_2S_4O_6$

Question 22.

(i) Dihydrogen reacts with dioxygen to form water. Name the product and write its formula when the isotope of hydrogen, which has one proton and one neutron in its nuclus, is treated with dioxygen?

(ii) Will the reactivity of both the isotopes of hydrogen be the same towards oxygen ? Justify your answer.

Question 23.

(i) Beryllium sulphate and magnesium sulphate are readily soluble in water whereas the sulphates of barium, calcium and strontium are only sparingly soluble. Explain.

(ii) Why is the temperature maintained around 393 K during the preparation of plaster of paris?

Question 24. Give the reactions involved in the preparation of propane from the following :

(i) $CH_3—CH = CH_2$

(ii) $CH_3 CH_2 CH_2 Cl$

(iii) $CH_3 CH_2 CH_2 COO^– Na^+$

Question 25. Assertion (A) : The first ionization enthalpy of alkali metals decreases down the group.

Reason (R) : Increase in number of orbitals increases the shielding effect which outweighs the increasing nuclear charge, therefore, the removal of outermost electron requires less energy on moving down the group.

(i) A and R both are correct but R is not the explanation of A.

(ii) A is false but R is correct.

(iii) A and R both are correct and R is the correct explanation of A.

(iv) A and R both are incorrect.

Question 26. Assertion (A) : Nitration of benzene requires the use of concentrated sulphuric acid and nitric acid.

Reason (R) : The mixture of acids produces the electrophile for the reaction.

(i) A and R both are correct but R is not the explanation of A.

(ii) A is false but R is correct.

(iii) A and R both are correct and R is the correct explanation of A.

(iv) A and R both are incorrect.

Question 27. Assertion (A) : Ozone is destroyed by solar radiations in upper stratosphere.

Reason (R) : Thinning of ozone layer allows excessive UV radiations to reach the surface of earth.

(i) A and R both are correct but R is not the explanation of A.

(ii) A is false but R is correct.

(iii) A and R both are correct and R is the correct explanation of A.

(iv) A and R both are incorrect.

Question 28.

(a) Liquids can be considered as very dense gases. When a liquid phase changes to gas phase, the liquid and the gas phases are in equilibrium and a surface separates the two phases. This surface is visible if both phases are in equilibrium and are below critical tempertaure and pressure. However, it is possible to interconvert liquid and gas wherein two phases are never present together.

With the help of a well-labled diagram show that $CO_2$ gas can be liquified by changing the pressure and temperature without passing through the situation when both gaseous and liquid $CO_2$ are at equilibrium.

(b) Arrange the following liquids in increasing order of their viscosities. Give reason for your answer.

Water, benzene, ethane-1,2-diol.

Question 29.

(a) Explain why :

(i) $BCl_3$ is a Lewis acid.

(ii) Boric acid is a monobasic acid.

(b) Compound ‘A’ of boron reacts with excess $NH_3$ to give a compound ‘B’. Compound ‘B’ on heating gives cyclic compound ‘C’. Compound C is called inorganic benzene.

(i) Identify compounds ‘A’, ‘B’ and ‘C’

(ii) Give the reactions involved in these processes.

Question 30.

(a) Write two important differences between inductive and resonance effects.

(b) Give reasons to explain the following observations:

(i) Carbon number ‘2’ in $CH_3CH_2Cl$ has more positive charge than that in $CH_3CH_2Br$.

(ii) $CH_3–CH = CH–CH = CH_2$ (I) is more stable than $CH_3–CH = CH–CH_2–CH = CH_2$ (II).