22.5 mL of an [tex]$HNO_3$[/tex] solution were titrated with 31.27 mL of a [tex]$0.167 M Ca(OH)_2$[/tex] solution to reach the equivalence point. What is the molarity of the [tex][tex]$HNO_3$[/tex][/tex] solution?

[tex]\[
2 HNO_3 + Ca(OH)_2 \rightarrow Ca(NO_3)_2 + 2 H_2O
\][/tex]

Hint: Did you account for the mole ratio?

Molarity (mol/L): ______



Answer :

Let's go through the solution step-by-step:

1. Convert volumes to liters:
- Volume of [tex]\( \text{HNO}_3 \)[/tex] in liters:
[tex]\[ 22.5 \, \text{mL} = 22.5 \, \text{mL} \times \frac{1 \, \text{L}}{1000 \, \text{mL}} = 0.0225 \, \text{L} \][/tex]

- Volume of [tex]\( \text{Ca(OH)}_2 \)[/tex] in liters:
[tex]\[ 31.27 \, \text{mL} = 31.27 \, \text{mL} \times \frac{1 \, \text{L}}{1000 \, \text{mL}} = 0.03127 \, \text{L} \][/tex]

2. Calculate the moles of [tex]\( \text{Ca(OH)}_2 \)[/tex]:
- Molarity of [tex]\( \text{Ca(OH)}_2 \)[/tex] is given as [tex]\( 0.167 \, \text{M} \)[/tex]:
[tex]\[ \text{moles of Ca(OH)}_2 = \text{Molarity} \times \text{Volume in liters} \][/tex]
[tex]\[ \text{moles of Ca(OH)}_2 = 0.167 \, \text{M} \times 0.03127 \, \text{L} = 0.00522209 \, \text{mol} \][/tex]

3. Using the balanced chemical equation to find moles of [tex]\( \text{HNO}_3 \)[/tex]:
- The balanced chemical equation is:
[tex]\[ 2 \text{HNO}_3 + \text{Ca(OH)}_2 \rightarrow \text{Ca(NO}_3\text{)}_2 + 2 \text{H}_2\text{O} \][/tex]
- This equation shows that 2 moles of [tex]\( \text{HNO}_3 \)[/tex] react with 1 mole of [tex]\( \text{Ca(OH)}_2 \)[/tex]. Therefore, the mole ratio of [tex]\( \text{HNO}_3 \)[/tex] to [tex]\( \text{Ca(OH)}_2 \)[/tex] is 2:1.
[tex]\[ \text{moles of HNO}_3 = 2 \times \text{moles of Ca(OH)}_2 \][/tex]
[tex]\[ \text{moles of HNO}_3 = 2 \times 0.00522209 \, \text{mol} = 0.01044418 \, \text{mol} \][/tex]

4. Calculate the molarity of [tex]\( \text{HNO}_3 \)[/tex]:
- Molarity is defined as the number of moles of solute per liter of solution:
[tex]\[ \text{Molarity of HNO}_3 = \frac{\text{moles of HNO}_3}{\text{volume of HNO}_3 \text{ in liters}} \][/tex]
[tex]\[ \text{Molarity of HNO}_3 = \frac{0.01044418 \, \text{mol}}{0.0225 \, \text{L}} = 0.4641857777777778 \, \text{M} \][/tex]

Therefore, the molarity of the [tex]\( \text{HNO}_3 \)[/tex] solution is approximately [tex]\( 0.464 \, \text{M} \)[/tex].