CHEMISTRY 1412 DR.E.OLIN 24) For the reaction H, (g) + S (s)-. H,sg. AH 20.2 krm
ID: 695432 • Letter: C
Question
CHEMISTRY 1412 DR.E.OLIN 24) For the reaction H, (g) + S (s)-. H,sg. AH 20.2 krmol and AS--+43.1 )/Krmo. Which of these statements is true? a) The reaction is only spontaneous at low temperatures b) The reaction is spontaneous at all temperatures. c) Go becomes less favorable as temperature increases. d) The reaction is spontaneous only at high temperatures. e) The reaction is at equilibrium at 25°C under standard conditions. 5) CalculateG" (in kl/mol) for the reaction 3NO2 (g) + H2O (l) 2HNO,() + NO (g) H2o (I) HNO3 (I) NO (g) NO2 (g) -237.2 -79.9 86.7 51.8 )8.7 b) 192 c) -414 d) -192 e)-155Explanation / Answer
24.
dH0 = - 20.2 kJ/mol = - 20200 J/mol
dS0 = - 20.2 kJ/mol = + 43.1 J/mol
We know that
dG0 = dH0 - T dS0
= (- 20200 J/mol) – T (+ 43.1 J/mol)
So, from the above equation we can see that, the higher the value of T, dG0 will be more negative. When dG0 value is negative, the reaction is spontaneous.
Hence, option is (d)
25.
3NO2(g) + H2O(l) ------> 2HNO3(l) + NO(g)
The above reaction equation is a balanced reaction equation.
So,
dG0 = sum of dG0 (products) - dG0 (reactants)
= [ 2 dG0(HNO3) + dG0(NO) ] - [ 3 dG0(NO2) + dG0(H2O) ]
= [ 2 (- 79.9) + 86.7] - [ 3 (51.8) + (- 237.2) ]
= [ - 159.8 + 86.7] - [ 155.4 - 237.2) ]
= - 73.1 – (- 81.8)
= - 73.1 + 81.8
= 8.7 J/K.mol
Answer is option (a)