Calculating Ph And Poh Worksheet With Answers Page 2
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1
2Solutions
+
-
Note: The significant figures in the concentration of [H
] or [OH
] is equal to the number of
decimal places in the pH or pOH and vice versa.
1)
What is the pH of a 0.0235 M HCl solution?
+
pH = -log[H
] = -log(0.0235) = 1.629
2)
What is the pOH of a 0.0235 M HCl solution?
+
pH = -log[H
] = -log(0.0235) = 1.629
pOH = 14.000 – pH = 14.000 – 1.629 = 12.371
-3
3)
What is the pH of a 6.50 x 10
M KOH solution?
-
-3
pOH = -log[OH
] = -log(6.50 x 10
) = 2.187
pH = 14.000 – pOH = 14.000 – 2.187 = 11.813
-3
-4
4)
A solution is created by measuring 3.60 x 10
moles of NaOH and 5.95 x 10
moles of
HCl into a container and then water is added until the final volume is 1.00 L. What is
the pH of this solution?
Since there is both acid and base we will assume a 1 mole acid:1 mole base ratio of
neutralization. There is more base than acid so the leftover base is what will affect
the pH of the solution.
-3
-4
-3
3.60 x 10
moles - 5.95 x 10
moles = 3.01 x 10
moles NaOH
-3
-3
3.01 x 10
moles NaOH = 3.01 x 10
M NaOH
1.00 L soln
-
-3
pOH = -log[OH
] = -log(3.01 x 10
) = 2.521
pH = 14.000 – pOH = 14.000 – 2.521 = 11.479
-5
5)
What is the pH of a 6.2 x 10
M NaOH solution?
-
-5
pOH = -log[OH
] = -log(6.2 x 10
) = 4.21
pH = 14.00 – pOH = 14.00 – 4.21 = 9.79
+
-7
6)
A solution with a H
concentration of 1.00 x 10
M is said to be neutral. Why?
+
-7
pH = -log[H
] = -log(1.00 x 10
) = 7.000
pOH = 14.000 – pH = 14.000 – 7.000 = 7.000
-
-
-
pOH = -log[OH
] = -log(OH
) = 7.000 we can use this to find the OH
concentration
-
-log[OH
] = 7.000
-
-1
log[OH
]
= 7.000
-
-1
log[OH
]
7.000
10
= 10
-
-1
7.000
[OH
]
= 10
7.000
1
= 10
-
[OH
]
-
-7
[OH
] = 1.00 x 10
M
+
-
The concentrations of H
and OH
are equal, as are the pH and pOH, so the solution
must be neutral.
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