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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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Universidad Tecnolgica Metropolitana
Qumica Industrial
Qumica General II
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SOLUCIONES Gua de Ejercicios de pH
1. Cul es el pH de 250 mL de:a) KOH 0.45 M
pOH = log OH pH = 14 pOH
pOH = log 0.45 pH = 14 0.34
pOH = 0.34 pH = 13.66
b) Ca(OH)2 0.078 M
+2
20.078 M 2 0.078 M0.078 M
0.156 M
Ca(OH) Ca 2 OH
pOH = log OH pH = 14 pOH
pOH = log 0.156 pH = 14 0.80
pOH = 0.80 pH = 13.20
c) HClO4 0.068 M
+pH = log H
pH = log 0.068
pH = 1.16
d) HNO3 0.045 M
+pH = log H
pH = log 0.045
pH = 1.34
2. Cul es el pH de 300 mL de:a) CH3COOH 0.066 M
5
aK 1.75 10
3 3
3
e e a
3
CH COOH CH COO H
0 0 0
0.066 M
CH COO HK K K
CH COOH
Si
Sf x x x
25
6 2
6
3
1.75 10 0.066
1.155 10
1.155 10
1.07 10 M
x
x
x
x
x
+
3
pH = log H
pH = log 1.07 10
pH = 2.97
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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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Universidad Tecnolgica Metropolitana Dallits Sagredo Oyarce
Qumica Industrial
Qumica General II
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b) HNO2 0.68 M4
aK 4.5 10
2 2
2
e e a
2
HNO H NO
0 0 0
0.68 M
H NOK K K
HNO
Si
Sf x x x
24
4 2
4
4.5 100.68
3.06 10
3.06 10
0.017 M
x
x
x
x
x
+pH = log H
pH = log 0.017
pH = 1.76
c) NH3 0.024 M5
bK 1.8 10
4 4
4
e e b
4
NH OH NH OH
0 0 0
0.024 M
NH OHK K K
NH OH
Si
Sf x x x
25
7 2
7
4
1.8 100.024
4.32 10
4.32 10
6.57 10 M
x
x
x
x
x
4
pOH = log OH pH = 14 pOH
pOH = log 6.57 10 pH = 14 3.18
pOH = 3.18 pH = 10.82
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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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Universidad Tecnolgica Metropolitana Dallits Sagredo Oyarce
Qumica Industrial
Qumica General II
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3. Cul es el pH de 100 mL de solucin que tiene disuelto:a) 0.7 mL de HCl gm m mL32 % 1,19
33
1.19 gc 32 gp0.83 gc 0.26 gp
1 mL 0.7 mL 100 gc 0.83gc
1 mol 7.12 10 moles7.12 10 moles 0.0172 M
36.5 g 0.26 gp 100 mL 1000 mL
x x
x x
+pH = log H
pH = log 0.0172
pH = 1.76
b) 0.4 g de NaOH, de un m m90 %
3
3
90 gp 1 mol0.36 gp 9 10 moles
100 gc 0.4 gc 40 g 0.36 gp
9 10 moles0.09 M pOH = log OH pH = 14 pOH
100 mL 1000 mL
pOH = log 0.09 pH = 14 1.04
pOH = 1.04 pH = 12.96
x x
x
c) 0.8 mL de NH3 5gm m mL b62 % 0.9 K 1.8 10
0.9 gc 62 gp0.72 gc 0.44 gp
1 mL 0.8 mL 100 gc 0.72gc
1 mol 0.025 moles0.025 moles 0.25 M
17 g 0.44 gp 100 mL 1000 mL
x x
x x
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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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Universidad Tecnolgica Metropolitana Dallits Sagredo Oyarce
Qumica Industrial
Qumica General II
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4 4
4
e e b
4
NH OH NH OH
0 0 0
0.25 M
NH OHK K K
NH OH
Si
Sf x x x
25
6 2
6
3
1.8 100.25
4.5 10
4.5 10
2.12 10 M
x
x
x
x
x
3
pOH = log OH pH = 14 pOH
pOH = log 2.12 10 pH = 14 2.67
pOH = 2.67 pH = 11.33
d) 1.4 mL de CH3COOH 5gm m mL a90 % 1.09 K 1.75 10
1.09 gc 90 gp1.52 gc 1.36 gp
1 mL 1.4 mL 100 gc 1.52gc
1 mol 0.02 moles0.02 moles 0.2 M
60 g 1.36 gp 100 mL 1000 mL
x x
x x
3 3
3
e e a
3
CH COOH CH COO H
0 0 0
0.2 M
CH COO HK K K
CH COOH
Si
Sf x x x
2
5
6 2
6
3
1.75 100.2
3.5 10
3.5 10
1.87 10 M
xx
x
x
x
+
3
pH = log H
pH = log 1.87 10
pH = 2.72
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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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4. Cul es la M de una solucin de:a) HCl de pH = 3.7 4H 1.99 10 M
b) HNO3 de pH = 2.5 3H 3.16 10 M
c) KOH de pH = 13.2
pOH = 14 pH
pOH = 14 13.2
pOH = 0.8
OH 0.15M
d) NaOH de pH = 12.8
pOH = 14 pH
pOH = 14 12.8
pOH = 1.2
OH 0.063M
e) NH3 de pH = 8.35
bK 1.8 10
6
pOH = 14 pH
pOH = 14 8.3
pOH = 5.7
OH 1.99 10 M
4 4
6 6
4
e e b
4
NH OH NH OH
1.99 10 M 1.99 10 M
NH OH
K K KNH OH
Sf x
2
6
5
12
45
7
4
1.99 101.8 10
3.96 10NH OH
1.8 10
NH OH 2.2 10 M
x
x
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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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f) CH3COOH de pH = 4.95
aK 1.75 10
5H 1.25 10 M
3 3
5 5
3
e e a
3
CH COOH CH COO H
1.25 10 M 1.25 10 M
CH COO HK K K
CH COOH
Sf x
2
5
5
10
35
6
3
1.25 101.75 10
1.56 10CH COOH
1.75 10
CH COOH 8.91 10 M
x
x
5. Cul es la concentracin:a) v v% de 300 mL de solucin que tiene disuelto 2 mL de etanol
v v
2 mL EtOH
0.66 %300 mL soluc 100 mL soluc
x
b) m v% de 200 mL de agua que disuelve 0.4 g de NaNO3
3 mv
0.4 g NaNO0.19 %
200.4 mL soluc 100 mL soluc
x
c) m m% de 1200 g de solucin que tiene disuelto 30 g de CuSO4
4 m
v
30 g CuSO
2.5 %1200 g soluc 100 g soluc
x
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8/2/2019 SOLUCIONES Gua de Ejercicios pH
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Universidad Tecnolgica Metropolitana Dallits Sagredo Oyarce
Qumica Industrial
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6. Cul es el pH de una mezcla:a) 200 mL HCl 0.035 M + 300 mL de HCl 0.066 M
0.035 moles 0.007 moles HCl1000 mL 200 mL
x 0.066 moles 0.0198 moles HCl1000 mL 300 mL
x
0.007 moles HCl + 0.0198 moles HCl = 0.0268 moles HCl
200 mL solucin + 300 mL solucin = 500 mL solucin
+
0.0268 moles HCl0.053 M
500 mL 1000 mL
pH = log H
pH = log 0.053
pH = 1.27
x
b) 48 mL NaOH 0.1 M + 100 mL NaOH 0.5 M + 50 mL de agua
0.1 mol0.0048 moles NaOH
1000 mL 48 mL
x
0.5 moles0.05 moles NaOH
1000 mL 100 mL
x
2
0.0048 moles NaOH + 0.05 moles NaOH = 0.0548 moles NaOH
48 mL solucin + 100 mL solucin + 50 mL H O = 298 mL solucin
0.0548 moles NaOH0.18 M
298 mL 1000 mL
pOH = log OH pH = 14 pOH
pOH = log 0.18 pH = 14 0.74
pOH = 0.74 pH = 13.26
x