Question

Question 25 (1 point) For the reaction N2(g) + 3H2(g) + 2NH3(e) R = 8.3145 J/mol DGº - - 32.8 kJ at 25° C; Calculate K, at 25°C. 1) 1.5 x 10-6 2) 5.61 x 105 3) 2.2 x 101 4) 4.6 O 5) 1.3 x 104

Answer 1

Kp can be found using the equation:-

DGo = - RTln(Keq)---------------------------------------(a)

Here,

DGo = Standard Gibb's free energy = -32.8 kJ = -32800 J -----(Given)

R = Universal Gas constant = 8.3145 J/mol.K -----(Given)

T = Temperature = 25o C = 25 + 273 K = 298 K -----(Given)

Keq = Equilibrium Constant

N2(g) + 3H2(g) <--------> 2NH3(g)

Here, we can se that the reaction is taking place in gaseous state. Therefore, we can use Kp in place of Keq in equation(a). Thus, equation(a) can be written as-

DGo = - RTln(Kp)---------------------------------------(b)

putting all the values in equation(b), we get-

-32800 = - 8.3145(298)ln(Kp)

32800 = 2477.721ln(Kp)

(32800/2477.721) = ln(Kp)

13.238 = ln(Kp)

Kp = e^(13.238)

Kp = 561277.9447

Kp = 5.61 X10^5

Out of all the given option our calculated value of Kp matches with option 2.

Hence, option 2 is the correct answer and rest of the options are wrong.