Chemistry-7.Half Course Test-2-Questions

HALF COURSE TEST - II (MAILING) CHEMISTRY Time: Two Hours Maximum Marks : 100 Note: i) This paper has TEN questions. ii) Separate answers are to be given on the separate pages. iii) Attempt all questions. iv) Use of logarithmic table is PERMITTED v) Use of calculator is NOT PERMITTED Useful Data: Gas Constant R = 8.314 J mol−1 K−1 = 0.0821 lit atm mol−1 K−1 = 2 Cal mol−1 Avogadro's Number Na = 6.023 × 1023 \Planck’s constant h = 6.625 × 10−34 J sec. 1 Faraday = 96500 Coulomb 1 calorie = 4.2 Joule Atomic No: Ca = 20, C = 6, O = 8, K = 19, Cl = 17, N = 7, S = 16, Na = 11, Cu = 29, Co =27, Mn = 25. Atomic Masses: Ag =108, Mn = 55, Cr = 52, Ca = 40, C = 12, O = 16, K = 39, Cl = 35.5, N = 14, S = 32, Na = 23, H = 1, I = 127, Mg = 24, Ne = 20, Br = 80, I = 127, As = 75, Cu = 63.54 Name : ☐☐☐☐☐☐☐☐☐☐☐☐☐☐☐☐☐ Enrol No. : ☐☐☐☐☐☐☐☐☐☐☐☐☐ 1. A piece of charcoal from the ruins of a settlement in Japan was found to have 14C/12C ratio that was 0.617 times that found in living organisms. How old is this piece of charcoal? Given the half life of 14C is 5570 years. [8] 2. At 300 K the specific rate constant for hydrolysis of ethyl ester by alkali is 6.36 litre mol–1 min–1. Starting with concentration of base and ester as 0.01 M what proportion of ester will be hydrolysed in 20 minutes? [8] 3. Sulphide ions in alkaline solution react with solid sulphur to form polyvalent sulphide ions. The equilibrium constant for the formation of S22– and S32– from S and S2– ions are 1.7 and 5.1 respectively. Calculate equilibrium constant for the formation of S32– from S2–2 and S. [8] 4. 0.16g of N2H4 are dissolved in water and the total volume made upto 500 ml. Calculate the percentage of N2H4 that has reacted with water in this solution. The Kb for N2H4 is 4 × 10–6M. [6] 5. The electron in the first excited state of H-atom absorbs a proton and is further excited. The Debroglie wavelength of the electron in this excited state is 13.4 Å. Calculate the wavelength of photon absorbed by the atom and also longest wave length radiation emitted when this electron de-excited to ground state. [8] 6. The percentage by volume of C3H8 in a mixture of C3H8, CH4 and CO is 36.5. Calculate the volume of CO2 produced when 100 ml of the mixture is burnt in excess of O2. [6] 7. A mixture of Na2C2O4 and KHC2O4.H2C2O4 required equal volumes of 0.1M KMnO4 and 0.1M NaOH separately. What is the molar ratio of Na2C2O4 and KHC2O4.H2C2O4 in the mixture? [7] 8. i) Predict the hybridisation and draw the structure of the following compounds (a) XeOF4, (b) PCl3Br2, (c) PCl2Br3, (d) XeF4 [2×4] ii) Arrange the following as indicated (a) NH3, PH3, AsH3, SbH3 (increasing bond angle) [2] (b) MgCO3, BaCO3, CaCO3, BeCO3 (increasing stability) [2] 9. The decomposition of a compound P, at temperature T according to the equation 2P(g) ⎯→ 4Q(g) + R(g) + S(l) is a first order reaction. After 30 minutes from the start of decomposition in a closed vessel, the total pressure developed is found to be 317 mmHg. After a long period of time the total pressure observed is found to be 617 mmHg. Calculate the half life time of the reaction, if the volume of liquid S is supposed to be negligible. (vapour pressure of S(l) at temperature T = 32.5 mmHg) [10] 10. What is the molar solubility of AgCl (s) in 0.100 M NH3 ? given that Ksp AgCl = 1.8 × 10-10 Kf [Ag(NH3)2]+ = 1.6 × 107 [8] 11. a) Butane 2,3 dione almost exclusively exists in keto form whereas cyclopentane 1,2 dione exists exclusively in enol form. Explain. [4] b) Arrange in the increasing acidic strength. [3] 12. Complete the following reaction with appropriate reagents. i) [3] [2] ii) [3] 13. Bring about the following conversions a) b) [4+2] 6

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