Chapter 4. Inorganic Carbon
Answers to Questions

1.  Diamond is harder than graphite because it has covalent bonds in 3 dimensions, while graphite has covalent bonds in only 2 dimensions and van der Waals forces in the third dimension.

2.

 
 

4. The completely delocalized p-manifold in the 2-D sheets of sp2 graphite conducts electricity well.  The other dimension does not.
 

5.

(a) Al4C3(s) + 6 H2O(l)  3 CH4(g) + 2 Al2O3(s)

(b) CaC2(s) + 2 H2O(l)  C2H2(g) + Ca(OH)2(s)

(c) HCO3-(aq) + H+(aq)  “H2CO3”   H2O + CO2

(d) NaOH(aq) + CO2(g)  NaHCO3

(e) CH4(g) + H2O(l)  CO(g) + 3 H2(g)             requires Ni catalyst and 1000 oC

6.

7. J. H. van’t Hoff, 1874.

8. buckyball has so much trapped space that it is likely to be less dense than the other two allotropes.

9.

 (a) (4 points) Yes! See below:
2 CO(g)  2 C(s) + O2(g)         DH = +221 kJ         DS = -179 J/deg
C(g) + O2(g)  CO2(g)             DH = -394 kJ         DS = +3 J/deg
2 CO(g)  C(s) + CO2(g)         DH = -173 kJ         DS = -176 J/deg
 (b) enthalpy favored and entropy not-favored; therefore, the reaction is spontaneous under low temps ( T < 983 K)

 (c) No, kinetics must be considered


10.

 (a) Al4C3
 (b) K2C2O4
 (c) CO(NH2)2
(d) H2CO3
(e) CaC2
(f) C2H2


11.
 Solubility of CO2 is 3.48 g/L at 0 oC, according to the text.
 

nCO2 = 3.48 g/44 g mol-1 = 0.079 mol
V = nRT/P

   = (0.079 mol) (0.0821 L atm mol-1 K-1) (273) K / 1 atm

   = 1.77 L CO2


12.

t1/2 = 0.693/k
k = 0.693/t1/2 = 0.693/5730 yrs = 1.21 x 10-4 yr-1
ln(N0/Nt) = kt

ln (15.3/8.2) = 1.21 x 10-4 yr-1 t

t = 5155 years old


13.


14.

P V = n R T

P V = (m/MM) R T

P MM = (m/V) R T

P MM = d R T

d = P MM / R T

dN2 = P MM / R T = (1) (28) / (0.0821) (298) = 1.144 g/L

dCH4 = P MM / R T = (1) (16) / (0.0821) (298) = 0.654 g/L

% lighter = 100% x (1.144 - 0.654) / 1.144 = 43%
 
 

15.
CO(g) + H2O(g)    CO2(g) + H2(g)

 DHorxn = -41 kJ  [requires Fe2O3 catalyst and 400 oC]


16.
 Synthesis gas is a mixture of CO and H2.  It is made by the reaction:

CH4(g) + H2O(g)   CO(g) + 3 H2(g) 

DHorxn = +206 kJ  [requires Ni catalyst,1000oC]


17. (a) D3h; (b) Dinfinity-h;  (c) D2h;  (d) Cinfinity-v