GSEB Std 11 Science Question Paper 2020 Chemistry (English Medium)

UNIT TEST STANDARD -11 Total Marks : 25 SUBJECT-CHEMISTRY Time: 1 Hour CODE-052 Medium: English SECTION A  Answer the following Q1 to Q7 as directed. (Each question is of 1 mark). [07] 1. What would be the SI unit for the quantity pV 2T 2/n ? 2. The pressure of a 1:4 mixture of dihydrogen and dioxygen enclosed in a vessel is one atmosphere. What would be the partial pressure of dioxygen? (At mass: H = 1, O = 16) (A) 0.8×105 atm (B) 0.008 Nm–2 (C) 8×10 Nm 4 –2 (D) 0.25 atm 3. ΔU0of combustion of methane is – X kJ mol–1. The value of ΔH0 is (A) = ΔU0 (B) > ΔU0 (C) < ΔU0 (D) = 0 4. Given: N2(g) + 3H2(g)  2NH3(g) ; ΔrH0= –92.4 kJ mol–1 What is the standard enthalpy of formation of NH3 gas? 5. Write Oxidation number of oxygen in O2F2. 6. Which alkali metal ion has maximum degree of hydration? 7. Complete and balance the reaction: BeCl2 + LiAlH4  SECTION B  Answer any two of the following Q8 to Q10. (Each question is of 2 marks) [04] 8. What will be the pressure exerted by a mixture of 3.2 g of methane and 4.4 g of carbon dioxide contained in a 9 dm3 flask at 27 °C ? (At mass: H = 1, C = 12, O = 16) 9. Justify that the reaction: 2Cu2O(s) + Cu2S(s)  6Cu(s) + SO2(g) is a redox reaction. Also identify the species which acts as an oxidant and which acts as a reductant. 10. Give main points of diagonal relationship between Beryllium and Aluminium. SECTION C  Answer any three of the following Q11 to Q15. (Each question is of 3 marks) [09] 11. The combustion of one mole of benzene takes place at 298 K and 1 atm. After combustion, CO2(g) and H2O (l) are produced and 3267.0 kJ of heat is liberated. Calculate the standard enthalpy of formation, ΔfH0of benzene. Standard enthalpies of formation of CO2(g) and H2O(l) are –393.5 kJ mol–1 and –285.83 kJ mol–1 respectively. 1

12. Balance the following redox reaction by ion – electron method : Cr2O72- (aq) + SO2 (g)  Cr3+ (aq) + SO42- (aq) (acidic medium) 13. Balance the following redox reaction in basic medium by oxidation number method. P4 (s) + OH- (aq)  PH3 (g) + H2PO21- (aq) 14. Write main points showing anomalous behavior of Lithium. 15. Comment on each of the following observations: (a) The mobilities of the alkali metal ions in aqueous solution are Li+ < Na+ < K+ < Rb+ < Cs+ (b) Lithium is the only alkali metal to form a nitride directly. (c) E for M2+ (aq) + 2e– → M(s) (where M = Ca, Sr or Ba) is nearly constant. SECTION D  Answer any one of the following Q16 to Q17. (Each question carries 5 marks) [05] 16. Answer as asked: (i). Find out the value of equilibrium constant for the following reaction at 298 K. 2NH3(g) + CO2(g)  NH2CONH2 (aq) + H2O (l) Standard Gibbs energy change, ΔrG 0at the given temperature is –13.6 kJ mol–1 (2 marks) (ii). At 60°C, dinitrogen tetroxide is 50 per cent dissociated. Calculate the standard free energy change at this temperature and at one atmosphere. (3 marks) 17. Answer as asked: (i). Density of a gas is found to be 5.46 g/dm3 at 27 °C at 2 bar pressure. What will be its density at STP? (2 marks) (ii). Pay load is defined as the difference between the mass of displaced air and the mass of the balloon. Calculate the pay load when a balloon of radius 10 m, mass 100 kg is filled with helium at 1.66 bar at 27°C. (Density of air = 1.2 kg m –3 and R = 0.083 bar dm3 K–1 mol–1). (3 marks) ------------x-------------x------------ 2