What volume of 0.25 M hydrochloric acid is required to react completely with 40 mL of 0.50 M calcium hydroxide? - 40 mL - VCE - SSCE Chemistry - Question 7 - 2014 - Paper 1

Next, we need to know how many moles of hydrochloric acid (HCl) are required to react with the calcium hydroxide. The balanced chemical reaction is:

$$ext{Ca(OH)}_2 + 2 ext{HCl} ightarrow ext{CaCl}_2 + 2 ext{H}_2 ext{O}$$

From the reaction, we see that 1 mole of calcium hydroxide reacts with 2 moles of hydrochloric acid. Thus:

$$ext{Moles of HCl} = 2 imes ext{Moles of Ca(OH)}_2 = 2 imes 0.020 = 0.040 ext{ moles}$$

Finally, we use the moles of hydrochloric acid to find the required volume. Again applying the formula:

ext{Volume} = rac{ ext{Moles}}{ ext{Concentration}}

Substituting in our values:

ext{Volume of HCl} = rac{0.040 ext{ moles}}{0.25 ext{ M}} = 0.160 ext{ L} = 160 ext{ mL}

Thus, the volume of 0.25 M hydrochloric acid required is 160 mL.