Understanding [tex]pH[/tex] and Ion Concentrations

Use Table B in your Student Guide to answer the following questions about ion concentrations.

1. A solution with a [tex]pH = 13[/tex] has approximately how many moles of [tex]OH^{-}[/tex] ions per liter? [tex]\square[/tex]

2. How many moles of [tex]H^{+}[/tex] would this same solution have per liter? (Use the decimal form of your answer.) [tex]\square[/tex]

3. A different solution with an [tex]H^{+}[/tex] concentration of [tex]1.0 \times 10^{-4}[/tex] would have [tex]pH =[/tex] [tex]\square[/tex].



Answer :

Let's solve each part of the question step-by-step.

### Step 1: Find the hydroxide ion concentration \([OH^-]\) for a solution with pH = 13

The relationship between pH and the hydroxide ion concentration \([OH^-]\) is given by:
[tex]\[ [ \text{OH}^- ] = 10^{-(14 - \text{pH})} \][/tex]
For a solution with pH = 13:
[tex]\[ [ \text{OH}^- ] = 10^{-(14 - 13)} = 10^{-1} = 0.1 \][/tex]
So, the concentration of \([OH^-]\) is \(0.1\) moles per liter.

### Step 2: Find the hydrogen ion concentration \([H^+]\) for the same solution with pH = 13

The relationship between pH and the hydrogen ion concentration \([H^+]\) is given by:
[tex]\[ [ \text{H}^+ ] = 10^{-\text{pH}} \][/tex]
For a solution with pH = 13:
[tex]\[ [ \text{H}^+ ] = 10^{-13} \][/tex]
So, the concentration of \([H^+]\) is \(1 \times 10^{-13}\) moles per liter.

### Step 3: Find the pH of a solution with \([H^+] = 1.0 \times 10^{-4}\)

The relationship between \([H^+]\) and pH is given by:
[tex]\[ \text{pH} = -\log_{10}([ \text{H}^+ ]) \][/tex]
For a solution with \([H^+] = 1.0 \times 10^{-4}\):
[tex]\[ \text{pH} = -\log_{10}(1.0 \times 10^{-4}) = -(-4) = 4.0 \][/tex]
So, the pH of the solution is \(4.0\).

### Putting it all together:

1. The concentration of \([OH^-]\) ions in a solution with pH = 13 is \(0.1\) moles per liter.
2. The concentration of \([H^+]\) ions in the same solution is \(1 \times 10^{-13}\) moles per liter.
3. The pH of a solution with [tex]\([H^+] = 1.0 \times 10^{-4}\)[/tex] is [tex]\(4.0\)[/tex].

Other Questions