Question

2- Therro dynamics e that best completes the statement or answers the question TIPLE CHOICE. Choose the one alternative that best completes the at 1) The SI unit for pressure is the A) newton. B) pascal C) MM Hg D) atmosphere. 2) The mixing of different gases by random molecular motion with freque A) diffusion. B) Dalton's law. C) compressibility. D) effusion 3) Entropy is a measure of A) the rate of a reaction. C) molecular randomness. B) free energy D) the heat of a reaction. 4) For the reaction 3 C2H2(g) - C6H61) at 25°C, the standard enthalpy change is -631 kJ and the standard entropy change is -430 J/K. Calculate the standard free energy change at 25°C. A)-618 kJ B) 948 kJ C) -503 kJ D-1061 kJ 5) Which of the following statements is not true? A) A nonspontaneous process cannot be caused to occur. B) A highly spontaneous process need not occur rapidly. C) The reverse of a spontaneous reaction is always nonspontaneous. D) A spontaneous process always moves toward equilibrium. 6) Calculate AS for the following reaction N2()+2 02(g) 2 NO2() Species N2 (8) 02 (8) NO2 (8) 5, J/(K.mol) 191.5 205.0 240.0 A) -121.5 J/K B) 636.5 J/K C) 15.5J/K D) -156.5 J/K How many grams of XeF6 are required to react with 1.16 L of hydrogen gas at 2.46 atm and 45°C in the reaction shown below? XeF68) +3 H2g) - Xe(g) + 6 HF@) D) 7.30 g C) 80.4 g A) 8.92 8 (B) 26.8 8 Indx 119.3.48

Answer 1

1) The SI unit of pressure is the B) pascal. 2) The mixing of different gases by random molecular motion with frequent collisions is called A) Diffusion. 3) Etropy is a major of C) molecular randomness. 4) 4,H° = -631kJ and 4,5º = -430J/K, T = 298K AG = AH - TAS° = -631*10^3 -(-298*430) = -502.86 kJ = -503 kJ Hence answer is option C) -503kJ. 5) A highly sponataneous process need to occur rapidly. Hence answer is option B). 6) AS° = ASO (product) - AS° (reactant) = 2(240) - (191.5+2*205)= - 121.5 J/K. Hence answer is option A). 7) Assume H2 be an ideal gas: PV = nRT n = number of moles of H2 = (2.46atm*1.16L) / (0.08206*(273+45)) = 0.1094 moles As per the equation 3 moles of H2 reacts with 1 mole of XeF6. So 0.1094 moles of H2 requires = 0.1094/3 = 0.0365 moles of XeF6 Molar mass of XeF6 = 245.3 g/mol Hence mass of 0.0365 moles of X3F6 = 0.0365*245.3 = 8.92 g Answer is option A)>

8) AG = AH - TAS = -249*10^3 - (-298*278) = -166 kJ the -ve sign indicates reaction goes in forword direction and favours product. Answer is option C). 9) Unsaturated solution can dissolve more solute till it becomes saturated and hence answer is option B) I. 10) P1V1/P2V2 = T1/T2 T2 = T1 / (P1V1/P2V2) = 298 / (1*350/1*250) = 212.9 K = 212.9-273 = -60.1 °C Answer is option A). 11) P1V/P2V = T1/T2 P2 = P1(T2/T1) = 2.1*(268/293) = 1.92 atm

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