Homework #5

1) The law of conservation of matter is that matter is neither created nor destroyed.

2) Scientific law summarizes what has been learned by careful observation of nature.

3) These expressions can be misleading because, according to the conservation of matter, atoms are never 'used up' or 'thrown away'.

4) 
a. Not balanced.
Reactant side: Sn: 1, H: 1, F: 1
Product side: Sn: 1,  H: 2, F: 2
b. Not balanced. 
Reactant side: Si: 1, O: 2, C: 1
Product side: Si: 1, O: 1, C: 2
c. Balanced. 
Reactant side: Al: 1, O: 3, H: 6, Cl: 3
Product side: Al: 1, O: 3, H: 6, Cl: 3
5) 
a. The coefficient for hydrogen gas is 3.
b. The coefficient for NH3 gas is 2. 
c. The coefficient for nitrogen gas is 1. 

6) 
a. 1 WO3 + 3 H2 --> 1 W + 3 H2O
b. 2 PbS + 3 O2 --> 2 PbO + 2 SO2
c. 4 Fe + 3 O2 --> 2 Fe2O3

7) 
a. 1 Ca3(PO4)2 + 3 H2SO4 --> 2 H3PO4 + 3 CaSO4
b. 2 C8H18 + 25 O2 --> 16 CO2 + 18 H2O

8) 
a. Yes. 
Reactant side: Na, 2; S, 1; O, 4; K, 2; Cl, 1
Product side: Na, 2; S, 1; O, 4; K, 2; Cl, 1
b. No, when balancing equations, subscripts remain the same, but coefficients are altered to balance the equation. 
c. 1 Na2SO4 + 2 KCl --> 2 NaCl + 1 K2SO4

9)  It would take 400,000 seconds to spend one mole of dollars.

10) 
a. 32g
b. 48g
c. 100g
d. 58g
e. 180g

11) This is because a mol is a unit of measure. 

12) 
a. 1 atom.
b. 0.5 atoms. 
c. 0.1 atoms. 
d. about 0.03 atoms.