CBSE Sample Paper Class 11 – Chemistry (Term 2)
CBSE Sample Paper Class 11
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Read the following instructions carefully.
(i) There are 24 questions in this question paper with internal choice.
(ii) SECTION A – Q. No. 1 to 6 are very short answer questions carrying 2 marks each.
(iii) SECTION B – Q. No. 7 to 22 are short answer questions carrying 3 marks each.
(iv) SECTION C- Q. No. 23-24 are case study-based questions carrying 5 marks each.
Que 1. Write the name of intermolecular forces acting in the followings:
(i) Helium atom in liquid helium. ½
(ii) HCl molecules in liquidity HCl. ½
(iii) Water molecules in liquid water. ½
(iv) Helium items in HCl molecules. ½
Que 2. Calculate the density of ammonia (NH3), at 30°C and 5 bar pressure. (Atomic mass of N = 14, H = 1). 2
Que 3. (i) Arrange the following in increasing order of their hydration enthalpy.
Li+, Na+, K+, Rb+ 1
(ii) Complete the following reaction equation Na(s) + H2O(l) → 1
Que 4. (i) What correction is applied to obtain the pressure of dry gas with the total pressure & aqueous
(ii) At a particular temperature, why vapour pressure of acetone is less than that of ether? 1
Que 5. Calculate the temperature of 4.0 moles of gas occupying 5dm3 volume at 3.32 bar. (R= 0.083 bar dm3 k-1 mol-1). 2
Que 6. Which out of Li and Na has greater value for the following properties:
(i) Hydration enthalpy 1
(ii) Stability of hydride 1
CBSE Sample Paper Class 11
Que 7. Under what condition will a reaction be spontaneous in following indicating the role of temperature. (Assume that temperature is positive)
(i) Both ∆H and ∆S are positive 1
(ii) Both ∆H and ∆S are negative. 1
(iii) ∆H is negative and ∆S is positive. 1
Que 8. Define Hess’s Law of constant heat of summation with a suitable example. 1
(i) What is the sign of ∆H for
(a) Evaporation of liquid water into steam. 1
(b) Freezing of liquid water into ice. 1
Que 9. Give reason for following
(i) Solubility of alkaline earth metal hydroxide in water increases down the group. 1
(ii) Lithium is a stronger reducing agent than sodium while the first ionization enthalpy of lithium is greater than sodium. 1
(iii) Alkali metals are not found in Free State in nature. 1
Que 10. Give reason for following
(i) BCl3 is more stable than TlCl3. 1
(ii) BF3 behaves as Lewis acid. 1
(iii) Atomic radius of gallium is less than the atomic radius of aluminium. 1
Que 11. An element A when heated with oxygen gas then form its monoxide B and dioxide C, monoxide B is a powerful reducing agent and reduces ferric oxide into iron. Identify element A and its both oxide B and C. Out of gas B and C which is constituent of water gas and producer gas. Write all chemical reaction equations involved in the above processes. 3
Arrange the following as shown in the bracket
(i) CO2 SiO2 GeO2 SnO2 PbO2 (increasing order of acidic strength) 1
(ii) C-C, Si-Si, Ge-Ge, Sn-Sn (Increasing order of bond enthalpy) 1
(iii) C, Si, Ge, Sn, Pb (Decreasing order of first ionization enthalpy) 1
Que 12. (i) Write IUPAC name of CH3-CH=CH-CH2CH3 1
(ii) Write the all-possible geometrical isomers of C4H8. 1
(iii) Out of n-pentane, 2-methyl butane, and 2,2-dimethyl, propane which one has the highest boiling point and which one has the least boiling point. ½, ½
Que 13. What happens when (write only chemical equation)
(i) Ethyne passed through a red hot iron tube. 1
(ii) Ethene is allowed to react with ozone and hydrolyzed in presence of zinc. 1
(iii) Benzene reacts with conc. HNO3 in presence of concentrate H2SO4. 1
Que 14. How will you convert the following (write only chemical equation)?
(i) Ethyne to ethanol 1
(ii) Propene to 1-propanol 1
(iii) Benzene to acetophenone 1
Que 15. Using the bond energy of H2 = 435 KJ mol-1, Br2 = 192 KJ mol-1, HBr = 368 KJmol-1. Calculate enthalpy change for the reaction H2(g) + Br2(g) → 2HBr(g). 3
Que 16. (i) Why standard entropy of an elementary substance is not zero whereas the standard enthalpy of formation is taken as zero? 2
(ii) What is spontaneous change? Give one example. 1
Que 17. (i) Why is LiF almost insoluble in water whereas LiCl is soluble not only in water but also in acetone? 2
(ii) Why are lithium salts commonly hydrated and those of the other alkali ions usually anhydrous? 1
Que 18. Give the chemical reaction as evidence for each of the following observations.
(i) Tin (II) is a reducing agent whereas lead (II) is not. 1
(ii) Gallium (I) undergoes disproportionation reaction. 2
Que 19. (i) Why do Boron halides from addition compound with NH3? 1
(ii) Assign appropriate reason for each of the following observations: 2
(a) Anhydrous AlCl3 is used as a catalyst in many organic reactions.
(b) The decreasing stability of +3 oxidations states with an increasing atomic number in group 13.
Que 20. Explain Kolbe’s Electrolysis along with the mechanism. 3
Que 21. How can ethene be prepared from 3
(ii) Ethyl bromide
Que 22. (i) Out of ethylene and acetylene which is more acidic and why? 1
(ii) Arrange the following in the increasing order of C-C bond length- C2H6, C2H4, C2H2. 2
CBSE Sample Paper Class 11
SECTION – C
Que 23. Read the following passage and answer the questions that follow:
Equilibrium can be established for both physical and chemical processes and at the equilibrium rate of forwarding reaction and rate of the backward process are equal equilibrium constant KC is expressed as the concentration of products divided by the concentration of reactants each raised to stoichiometric coefficient. KC value has a fixed value of constant temperature and at this stage concentration pressure etc, become constant KP is the equilibrium constant in terms of partial pressure of gases or vapours. The direction of reaction can be predicted by reaction quotient QC and Qp, when QC is equal to KC or QP are equal to KP then equilibrium establishes. Le-Chatelier’s principle states equilibrium will shift in the direction so as to counterbalance the effect of change in temperature, pressure, and concentration. The equilibrium between ions and unionized molecules in the weak electrolytes is called ionic equilibrium.
Using the above case answer the following questions
(i) At a certain temperature Kp = 9/4 for the reaction
CO(g) + H2O(g) ⇌ CO2(g) + H2(g). if 10 moles of each of four gases are taken in 1 litre container, what will be the concentration of H2 gas at equilibrium.
In the reaction H2(g) + I2(g) ⇌ 2 HI(g) 2
(ii) At equilibrium if the concentration of the reactants increased what effect will be seen in the value of equilibrium constant Kc at a given temperature. 1
(iii) If the value of an equilibrium constant for a particular reaction is 1.6 × 1012 what will be the major component present in the system at equilibrium. 1
(iv) Equilibrium constant K1 for reaction 3H2(g) + N2(g) ⇌ 2NH3(g) is 49, what is equilibrium constant K2 for NH3(g) ⇌ N2(g) + 3/2 H2O(g). 1
Que 24. Arrhenius acids give H+ ion in aqueous solution whereas bases give OH– in aqueous solution. Bronsted acids are proton donors whereas Bronsted bases are proton acceptors. Acids, on donating proton form conjugate base whereas bases form conjugate acid after accepting a proton. A buffer solution is a solution whose pH does not change by adding a small amount of H+ or OH–. The decrease in conc. of one of the ions by adding another ion as the common ion is called the common ion effect. Lewis’s acids are electron deficient or + vely charged. Lewis bases are electron-rich or negatively charged. Ksp (solubility product) is the product of the molar concentration of ions raised to power the number of ions per formula of the compound is a sparingly soluble salt. Precipitation occurs only if the ionic product exceeds the solubility product. The solubility of salt decreases in presence of common ions. Kw is an ionic product of water, 1 × 10–14 at 298 K. Kw increases with an increase in temperature. pH is – log [H3O+] where [H3O+] = Cµ in monoprotic acid ‘C’ is molar conc., ‘µ’ is the degree of ionization. A salt is said to be hydrolyzed if the pH of the solution changes. KH is a hydrolytic constant. The pH of salts of strong acid and strong base is equal to 7. pH of other salts can be 7. pH of buffer solution can be calculated with the help of Henderson equation.
(i) What will be the conjugate base of (i) H2SO4 (ii) HCO3– 1
(ii) What are conjugate acids of (i) NH2– (ii) NH3 1
(iii) The conc. of [H3O+] is 4 × 10–4. What is pH of solution? [log 4 = 0.6021, log 10 = 1.3]. 3
CBSE Sample Paper Class 11