Page 345 - Theory and Problems of BEGINNING CHEMISTRY

334 PRACTICE QUIZZES

Chapter 17
1. NH 3 + H 2 O −− NH 4 + + OH −
−−
Initial: 0.100 0.200 0.000
Change: x x x
Final: 0.100−x 0.200 + x x
+
−
[NH 4 ][OH ] −5
K b = = 1.8 × 10
[NH 3 ]
(0.200)x
= = 1.8 × 10 −5
0.100
−
x = 9.0 × 10 −6 = [OH ]
−6
[H 3 O ] = K w /[OH ] = (1.0 × 10 −14 )/(9.0 × 10 ) = 1.1 × 10 −9
−
+
pH = 8.96
2. HC 2 H 3 O 2 + NaOH −→ NaC 2 H 3 O 2 + H 2 O
Assume that this acid-base reaction proceeds 100%, yielding 0.100 mol NaC 2 H 3 O 2 and leaving 0.150 mol HC 2 H 3 O 2
in excess. These are the initial concentrations for the equilibrium calculation.
− + H 3 O +
HC 2 H 3 O 2 + H 2 O −→ C 2 H 3 O 2
Initial: 0.150 0.100 0.000
Change: x x x
Final: 0.150 − x 0.100 + x x

+
−
[C 2 H 3 O 2 ][H 3 O ]
K a = = 1.8 × 10 −5
[HC 2 H 3 O 2 ]
(0.100)x −5
= = 1.8 × 10
0.150
x = [H 3 O ] = 2.7 × 10 −5
+
Chapter 18
1. (a) Alkane (hydrocarbon) (b) Alcohol (c) Ketone (d ) Amide (e) Ester
2. CH 3 CHOHCH 3 and CH 3 CH 2 OCH 3

3. CH 3 CH(NH 2 )CH 3 , CH 3 CH 2 NHCH 3 , and (CH 3 ) 3 N

Chapter 19
1. (a) 22 Na −→ 22 Ne + + β (a positron)
1
4
(b) 14 N + He −→ 17 O + H
1
1
94
(c) 235 U + n −→ 140 Ba + Kr + 2 n
m 0 0.693t 0.693t 100.0
2. ln = = = ln = 0.9163
m t 50.0 years 40.0
1/2
0.9163(50.0 years)
t = = 66.1 years
0.693