Part 1 Questions

1. H^-, examples: NaH, CaH2

2. (a) NaBH4; (b) LiAlH4; (c) CaH2

3.                     protons neutrons
     hydrogen        1              0
     deuterium      1              1
     tritium            1              2

4. abundance of deuterium: 1/6400

5. half-life = 12.5 years

6. hydrogen makes up 92% of all atoms in Universe and 73.9% of the Universe’s mass.

7. H2 is found as elemental hydrogen near volcanic areas, in water, H2S, amines and organic compounds.

8. example: Zn(s) + 2 HCl(aq)   H2(g) + ZnCl2(aq)

9. CH4 + H2O(g)    CO(g) + 3 H2(g) ("syn gas")
 or
 3 Fe(s) + 4 H2O   Fe3O4(s) + 4 H2

10. (1) synthesis of ammonia by Haber process; (b) hydrogenate vegetable oil to make margarine and greases; (c) to produce methanol (from syn-gas by the Fisher-Tropsch process)

11. (a)
 Broke 4 C-H bonds:  4 x + 413 kJ
 Broke 2 O-H bonds:  2 x + 467
 formed one CO triple:      - 1072
 Formed three H-H: 3 x - 432
 TOTAL     DHo = +218 kJ
 
 

11 (b) DHf:

 CH4          -74.8 kJ/mol
 H2O(g)     -241.8
 CO(g)       -110.5
 H2(g)              0

12.
 Broke 3 C-C bonds       2 x + 347 kJ
 Broke 2 C-H bonds       2 x + 413
 converted three C-C singles into C-C double bonds  3x+347 - 3 x 614
 Formed one H-H        1 x - 432
 TOTAL         DHo = +287 kJ

13. (a) H2⁺: (ss)¹(ss*)⁰     BO = 1/2;
(b) H2^-: (ss)²(ss*)¹         BO = 1/2;

14.
(a) CaH2(s) + H2O(l)   Ca(OH)2(s) + 2 H2(g)
(b) H2(g) + O2(g)   2 H2O(g)
(c) Na(s) + H2O(l)  2 NaOH(aq) + H2(g)
(d) C2H4(g) + H2(g)  C2H6(g)
(e) NaH(s) + HCl(aq)  NaCl(aq) + H2(g)
(f) K(s) + H2(g)  2 KH(s)

15. C(s) + H2O(g)   CO(g) + H2(g)

16. 0.99 g Mg

17. (a) dhydrogen = 0.0890 g H2/L;
(b) dair = 1.29 g H2/L;
(c) ratio = 14.5:1