1.

FeAsS     arsenopyrite

Bi₂S₃     bismuthinite

HgS     cinnabar

CoAsS     cobaltite

PbS     galena

MoS₂     molybdenite

FeS₂     pyrite

Sb₂S₃     stibnite

WS₂     tungstite

2. orthorhombic below 96 ^oC (cell lengths all unique and cell angles all 90 ^o); monoclinic above 96 ^oC (cell lengths all unique and two cell angles = 90 ^o and one cell angle < 90^o)

3. (a) S₂^-2; (b) O₂^-2; (c) persulfide

4. (a) fcc, therefore four FeS₂ units per unit cell
 (b) 551 pm
 (c) sketch fcc

5. soft; soft

6. starte to polymerize

7. Remember 1 ppm = 1 mg/kg and 1 ppb is 1 mg/1000 kg (or 1 mg/kg)
 Therefore 0.1 mg Po/1000 kg ore = 0.1 ppb Po

8.

9. q = -299 kJ

10. H₂O + SO₃^-2 + Br₂   2 Br^- + SO₄^-2 + 2 H⁺

11. Simply add the four equations as written this time:
 

S(s) + O₂(g)   SO₂(g) DH^o = -297 kJ

SO₂(g) + 1/2 O₂(g)  SO₃(g) DH^o = -98 kJ

SO₃(g) + H₂O(l)   H₂SO₄(l) DH^o = -230 kJ

H₂(g) + 1/2 O₂(g)   H₂O(l)  DH^o = -286 kJ
 

H₂ + S(s) + 2 O₂(g)   H₂SO₄(l)  DH^o = -911 kJ

12.

(a) high pressure and low temperature

(b) DS < 0

(c) use high temperature to increase the rate but not so high as to make it non-spontaneous.

13.