13. The standard molar entropy of lead(II) bromide (PbBr 2 ) is 161 J/mol K. Wha
ID: 773998 • Letter: 1
Question
13. The standard molar entropy of lead(II) bromide (PbBr2) is 161 J/mol K. What is the entropy of 2.45 g of PbBr2?
a.
+1.07 J/K
d.
161 J/K
b.
1.07 J/K
e.
0 J/K
c.
+161 J/K
14. Calculate DS0 for the formation of 1 mol of HI(g) from its elements given the following information:
S0[H2(g)] = 131 J/mol?K
S0[I2(s)] = 116 J/mol?K
S0[HI(g)] = 206 J/mol?K.
A) 82 J/K B) 165 J/K C) 247 J/K D) 329 J/K
15. For which reaction is DSsys > 0?
A) CH4(g) + 2 O2(g) ? CO2(g) + 2 H2O(l)
B) NH3(g) + HCl(g) ? NH4Cl(s)
C) 2 NH4NO3(s) ? 2 N2(g) + O2(g) + 4 H2O(g)
D) HCl(aq) + NaOH(aq) ? NaCl(aq) + H2O(l)
16. In a biochemical reaction, A + B C with ?G= 30 kJ/mol. Which of the following reactions might be effectively coupled to this reaction so that it becomes more spontaneous?
I.
C + D are the reactants, and B + E are the products
?G= -40 kJ/mol
II.
C + D are the reactants, and B + E are the products
?G= +40 kJ/mol
a.
I only
b.
II only
c.
I or II
d.
Neither I nor II can increase spontaneity.
e.
No coupling is required as the reaction is already spontaneous.
a.
+1.07 J/K
d.
161 J/K
b.
1.07 J/K
e.
0 J/K
c.
+161 J/K
Explanation / Answer
c.
+161 J/K
Given that;
The standard molar entropy of lead(II) bromide (PbBr2) is 161 J/mol K
Firsta calculate the number of moles 2.45 g of PbBr2
number of moles / molar mass
= 2.45 g of PbBr2/367.01 g/mol
= 0.0067 Moles
the entropy of 2.45 g of PbBr2 :
0.0067 Moles *161 J/mol K
= 1.075 161 J/ K
Thus the correct answer is a.
c.
+161 J/K
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