TECHNOLOGICAL INSTITUTE OF TH EPHILIPPINES COMPETENCY EXAM IN PHYSICAL CHEMISTRY STUDENT NUMBER _______________________________________ DATE__September 16, 2010___________ Direction: Write the letter that corresponds to the correct answer. 1. A gas mixture consists of 325 mg of methane, 175 mg of argon, and 225 mg of neon. The partial pressure of neon at 300K is 66.5 Torr. Calculate the volume of the mixture. a. 32 L b. 3.16 L c. 4.25L d. NOTG 2. The time of outflow of 250 ml methane in a porous opening is 16 seconds. Under the same condition of T and P, how long would it take 1500 ml of sulfur dioxide to diffuse through the same opening? (a) 129 sec (b) 192 sec (c) 229 sec (d) 291 sec 3. What is the change in molar enthalpy of nitrogen gas when it is heated from 25 degrees C to 100 degrees c? For nitrogen, a = 28.58, b/(10-2K-1) = 3.77 and C/(105K2)= -0.50 a. ∆H = 4.5 KJ b. 2.2 KJ c. 3.25 KJ d. NOTG 4 4. With regards to G, a system is more stable when 5 a) it is minimum (b) it is maximum (c) it is equal to zero (d) none of the above 5. The standard reaction enthalpy for the hydrogenation of propene is –124KJ/mole, The standard reaction enthalpy for the combustion of propane is –2220KJ/mole. Calculate the standard reaction enthalpy for the combustion of propene given that the heat of formation of liquid water is – 286 KJ/mole CH2=CHCH3(g) + H2O CH3CH2CH3(g) 6 a. – 1065 KJ b. – 2058 KJ c. – 3256 KJ d. NOTG 6. When 1.000 mole of glucose is oxidized to CO2 and H2O at 25 °C according to the equation: C6H12O6(s) + 6O2(g) 6CO2(g) + 6H2O(l). Calorimetric measurements give ΔU = -2608 KJ and ΔS = 182.4J /K at 25°C and standard condition. How much of this energy change can be extracted as work? a. –2965 KJ b. – 2862 KJ c. – 2653 KJ d. NOTG 7. The radius of a given capillary is 0.105 mm. A liquid whose density is 0.80 g/cc rises in this capillary to a height of 6.25 cm. Calculate the surface tension of the liquid. (a) 18.7 dynes/cm (b) 21.3 dynes/cm (c) 25.7 dynes/cm (d) 30.3 dynes/cm 8. The molar volume of benzene (l) is 88.9 cc at 20°C and 1 atm pressure. Find the value of ΔG for the compression of 1 mole of the liquid from 1 to 100 atm a. 210 calories b. 220 calories c. 230 calories d. NOTG 9. The standard free energy of formation of HCl(g) at 25 °C is – 22, 770 cal/mole. Calculate the thermodynamic equilibrium constant for the dissociation of HCl into its elements at 25 °C. a. 5.02 x 1016 b. 2.00 x 10-17 c. 3.02 x 1016 d. NOTG 10. A current of 0.452 ampere is passed through an electrolytic cell containing molten calcium chloride for 1.50 hours. The weight of calcium metal formed is: (Atomic mass of Ca = 40g/mole, Atomic mass of Cl = 35.45 g/mole) a. 1.014 g b. 0.2535g c. 0.507 g d. 0.7605 g 11. At 30oC Kp in atmosphere for dissociation SO2Cl2(g) = SO2 (g) + Cl2 (g) is 2.9 x 10-2. Calculate the degree of dissociation when the total equilibrium pressure is 1 atm. (a) 0.168 (b) 0.186 (c) 0.351 (d) 0.513 12. If the potential created by a chemical reaction is used to move a current, the cell created is called (a) concentration cell (c) electrolytic cell (b) galvanic cell (d) none of the above 13. A solution composed 10 grams of non-volatile organic solute in 100 grams of diethyl ether (CH 3CH2OCH2CH3) has a vapour pressure of 426.0 mm Hg at 20oC. If the vapor pressure of the pure diethyl ether is 442.2 mm Hg at the same temperature, what is the molecular weight of solute? (a) 149. 6 g/mole (b) 164.8 g/mol (c) 186.4 g/mol (d) 194.8 g/mol 14. Assuming CO2 to be ideal gas, calculate the work done by 10 g of CO 2 in expanding isothermally and reversibly from a volume of 5 liters to 10 liters at 27 oC. (a) 87.2 cal (b) 93.9 cal (c) 102.6 cal (d) 113.5 cal 15. Benzene and toluene form a solution which is very nearly ideal. Consider a mixture of benzene (Bz) and toluene (Tol) at 60o C. At 60o C the vapor pressures of pure benzene and pure toluene are 385 Torr and 139 Torr, respectively. what is the benzene composition of the vapor in equilibrium with this solution in a mixture with XBz = 0.400, and XTol = 0.600 a. 0.351 b. 0.649 c. 0.702 d. 0.288 16. Calculate the entropy suffered by 2 moles of an ideal gas on being heated from a volume of 100L at 50 oC to a volume of 150L at 150oC. For the gas, Cv = 7.88 cal/mol-oC. (a) 5.86 cal/K (b) 6.73 cal/K (c) 7.86 cal/K (d) NOTA 17. A mixture of 1.24 x 10 – 2 moles of H2(g) and 2.46 x 10 –2 moles of I2(g) was heated at 457.6 °C until equilibrium is attained. How many moles of HI (g) are present at equilibrium? K(eq) = 48.7 at said temperature for the reaction.
H2(g) + I2(g) 2HI(g) a. 0.0116 b. 0.0011 c. 0.00065 d. NOTG 7 18. An aniline – hexane pair at 30 °C gives 2 layers, one at 21.9% aniline and the other at 89.9% aniline. What will be the mass of the 2 layers when 10.95 grams of aniline and 39.05 grams of hexane are mixed at 30 °C? 8 a. 50 grams of hexane L, 0 grams of aniline L b. 25 grams of Hexane L, 25 grams of Aniline L 9 c. 15 grams of hexane L, 35 grams of Aniline L d. NOTG 19. Which among the following conditions of a system DOES NOT satisfy that U = q (a) if W= 0 (b) when the volume is constant (c) when the opposing pressure is zero (d) when the opposing pressure is constant 20. Calculate the osmotic pressure of a solution of urea that freezes at – 1.5 ˚C. a. 20 atm b. 19 atm c. 18 atm d. NOTG
Benzene and toluene form a solution which is very nearly ideal. Consider a mixture of benzene (Bz) and toluene (Tol) at 60o C. At 60o C the vapor pressures of pure benzene and pure toluene are 385 Torr and 139 Torr, respectively. What are the vapor pressures of benzene and toluene in a mixture with XBz = 0.400, and XTol = 0.600, and what is the composition of the vapor in equilibrium with this solution? Use Raoult's law to find the vapor pressures of the two species,
The total pressure is the sum of these two individual pressures, 237 Torr. The composition of the vapor phase is obtained from the vapor pressures and Dalton's law of partial pressures,
