Determine the molar mass of an unknown monoprotic acid to two decimal places if 16.98 mL of a 0.086 M NaOH solution were used to titrate 0.236 g of the unknown acid

Respuesta :

1 ) Chemical equation

[tex]\text{NaOH + HX}\rightarrow H_2O+Na^++X^-[/tex]

HX represents the unknown acid.

2) Moles of NaOH in the reaction

[tex]M=\frac{\text{moles of solute}}{\text{liters of solution}}[/tex]

Convert mL into L

[tex]L=16.98mL\cdot\frac{1L}{1000mL}=0.01698L[/tex]

Plug in known values in the equation and solve for moles.

[tex]0.086M=\frac{\text{moles of NaOH}}{0.01698L}[/tex][tex]\text{mol NaOH= 0.086M}\cdot0.01698L=0.00146028\text{ mol NaOH}[/tex]

3) Moles of the unknown acid that reacted with 0.00146028 mol NaOH

Molar ratio

1 mol NaOH: 1 mol HX

[tex]\text{mol HX=0.00146028 mol NaOH}\cdot\frac{1\text{ mol HX}}{1\text{ mol NaOH}}=0.00146028\text{ mol HX}[/tex]

4) Molar mass of the unknown monoprotic acid

[tex]\text{Molar Mass=}\frac{\text{mass of solute (g)}}{moles\text{ of solute}}[/tex]

Plug in known values and solve

[tex]\text{Molar Mass}=\frac{0.236\text{ g HX}}{0.00146028\text{ mol HX}}=161.61\text{ g/mol}[/tex]

The molar mass of the unknown monoprotic acid is 161.61 g/mol

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