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Find the pH for a solution of Ca(OH)_{2} with a molarity of 1.0 x 10^{-4}.

## Answer

[H^{+}][OH^{–}] = 1.0 x 10^{-14}

[H^{+}][2(1.0 x 10^{-4}] = 1.0 x 10^{-14}

[H^{+}] = 5.0 x 10^{-11}

pH = -log [H^{+}]

pH = -log [5.0 x 10^{-11}]

pH = 10

The letters “pH” represent the French words “pouvoir hydrogene” which means “hydrogen power”.

The definition of pH is pH is equal to the negative log (logarithm) of the _________ ion concentration of a solution.

## Answer

hydrogen

The logarithm of a number is the power to which 10 must be raised to equal that number.

A pH value of less than 7 indicates a(n) ____________ solution.

## Answer

acidic

A pH value of ________ indicates a neutral solution.

## Answer

7

A pH value of more than 7 indicates a(n) _______________ solution.

## Answer

basic

The greater the [H^{+}] concentration, the ________ the pH.

## Answer

lower

If a solution is _______________ the [H^{+}] concentration equals the [OH^{–}] concentration.

## Answer

neutral

An aqueous base has a pH of 8.1. Another has a pH of 10. Which solution has the larger concentration of [OH^{–}] ions?

**a.** The solution with a pH of 10 has a larger concentration of [OH^{–}] ions.

**b.** The solution with a pH of 8.1 has a larger concentration of [OH^{–}] ions.

## Answer

A.

Determine the pH of a 0.035M H_{2}SO_{4} solution.

## Answer

pH = -log [H^{+}] = -log [2(3.5 x 10^{-2}] = -(-1.2) = **1.2**

The pH of a 0.010M Mg(OH)_{2} solution is ______.

## Answer

[H^{+}][OH^{–}] = 1.0 x 10^{-14}

[H^{+}][2(1.0 x 10^{-2})] = 1.0 x 10^{-14}

[H^{+}] = 5.0 x 10^{-13}

pH = -log [H^{+}] = -log [5.0 x 10^{-13}] = -(-12.3)

pH = 12

What is the hydrogen ion concentration of an aqueous HCl solution that has a pH of 3.0?

## Answer

pH = -log [H^{+}

3.0 = -log [H^{+}]

[H^{+}] = 1.0 x 10^{-3} M

What is the hydroxide ion concentration of this same solution?

## Answer

[H^{+}][OH^{–}] = 1.0 x 10^{-14}

[1.0 x 10^{-3}][OH^{–}] = 1.0 x 10^{-14}

[OH^{–}] = 1.0 x 10^{-11} M

Which ion, H^{+} or OH^{–}, is in greater concentration?

## Answer

H^{+}

(1.0 x 10^{-3} is greater than 1.0 x 10^{-11})

Is this solution acidic or basic?

## Answer

Acidic