Question

If 20.0 mL of an 8.0 aqueous phosphoric acid solution is mixed with 2.0 mL of a 5.0 M aqueous solution of potassium hydroxide, what mass of water is generated?

Answer 1

Mixing 20.0 mL of 8.0 M phosphoric acid with 2.0 mL of 5.0 M potassium hydroxide generates approximately 0.398 g of water.

To find the mass of water generated when phosphoric acid (
`\(H_3PO_4\)`) reacts with potassium hydroxide (KOH), we first determine the moles of each reactant using their concentrations and volumes. The balanced chemical equation is:

`\[ H_3PO_4(aq) + 3KOH(aq) \rightarrow K_3PO_4(aq) + 3H_2O(l) \]`

Using the formula
`\(Molarity = \frac{\text{moles}}{\text{liters}}\)`, we find the moles of phosphoric acid and potassium hydroxide.

`\[ \text{Moles of } H_3PO_4 = 8.0 \, \text{M} * 0.020 \, \text{L} \]`

`\[ \text{Moles of } KOH = 5.0 \, \text{M} * 0.0020 \, \text{L} \]`

After finding the limiting reactant (the one with fewer moles), we determine the moles of water produced and convert it to grams using the molar mass of water (
`\(18.015 \, \text{g/mol}\)`).

The calculated mass of water generated is approximately
`\(0.398 \, \text{g}\).`