Question
LIL PIERS 18 & 19 ame: Adhem mawar Date: 1. What is As at 298 K for the following reaction? 20 (g) 302g) Substanc ufomol K) at 298. 2050 030g) 238.8 A) +137.4 JK B) 37.4 J/K C) +33.8 JK D) 33.8 JK E) +443.8 2. Which of the following is true for the reaction NH3 NHlg at 33 C and 1 atm pressure? The normal boiling point for N is 33 C) A) AH 0 B) AS m 0 E) AH TAS 3. What is the change in entropy when 0.195 g of silicon is burned in excess oxygen to yield silicon dioxide at 298 K? Si(s) Oig) Sio:(s): AS 82.4 JK at 298 K A) 35.6 J/K B) -2.63 x 10 JK C) -1.27 JK D) -182 J/K E) -4.25 x 10 JK
Explanation / Answer
Q1.
For
2O3 = 3O2
dS = Sproducts - Sreactants
dS = 3*205 - 2*238.8 =137 J/K
best answer is A
Q2.
dH cant be zero, nor dS
dG = 0, since it is in equilibrium
so
dG = dH - T*dS
0 = dH - T*dS
dH = T*dS
so choose E