4 Impure nickel, refined by smehing sulfide ores in a blast furnace, can be conv

Question

4 Impure nickel, refined by smehing sulfide ores in a blast furnace, can be converted into metal from 99.90% to 99.99% purity by the Mond process. The primary re- action involved in the Mond process is a. Without referring to Appendix 4, predict the sign of AS for the preceding reaction. Explain. b. The spontaneity of the preceding reaction is temperature-dependent. Predict the sign of ASu for this reaction. Explain. For Nico)4(g), JK mol1 at 298 K. Using these values and data in Appendix 4, calculate H° and ASe for the pre- ceding reaction. c. -_607 kJ/mol and s-417 : d. Calculate the temperature at which (K-1) for the preceding reaction, assuming that and AS. do not depend on temperature. e. The first step of the Mond process involves equili- brating impure nickel with COlg) and Ni(CO) at about 50C. The purpose of this step is to vert as much nickel as possible into the gas pha Calculate the equilibrium constant for the pr reaction at 50. C. f. In the second step of the Mond process, the gaseous Ni(CO), is isolated and heated at 22 The purpose of this step is to deposit as muc nickel as possible as pure solid (the reverse preceding reaction). Calculate the equilibri constant for the preceding reaction at 227 g. Why is temperature increased for the second stCP the Mond process? h. The Mond process relies on the volatility of Ni(CO)4 for its success, Only pressures and te atures at which Ni(CO)4 is a gas are useful At cently developed variation of the Mond process carries out the first step at higher pressures n temperature of 152eC. Estimate the maximum sure of Ni(CO)Alg) that can be attained before gas will liquefy at 152 The boiling point i(CO, is 42 C, and the enthalpy of vaporization 29.0 kJ/mol. [Hint: The phase-change reactión nd the corresponding equilibrium expression are CO)a(g) will liquefy when the pressure of Ni(CO) s greater than the Kp value.]

Explanation / Answer

Part a)

In the reaction Ni(s) + 4CO(g) Ni(CO)4(g) there is a decrease in the number of gaseous molecules. So spontaneity would decrease which indicates a decrease in entropy S < 0

Part b)

Ssurrounding = - H/T

Since this reaction is exothermic, heat is given off to the surroundings, and that extra heat increases the entropy of the surroundings. which indicates an increase in entropy S > 0

Part c)

Ni(s) CO(g) Ni(CO)4(g)

Hf ° 0 110.52 602.9

S298° 29.87 197.56 410.6

S°= -409.5 J/K and H° =160.8 kJ

Part d)

G = H – TS

at G = 0

H = TS

T = H / S

= 392.67 K

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