25cm3 of a 0.10moldm-3 solution of sodium hydroxide reacts exactly in a titration with 15cm3 HCl. What is the concentration of the hydrochloric acid?
First, write a balanced chemical equation to determine the ratio of the reacting species: NaOH + HCl --> NaCl + H2O Sodium hydroxide and hydrochloric acid react in a 1:1 ratio, so the number of moles of each is equal.Next, work out the number of moles of sodium hydroxide that react, using the n=cV equation. Remember to convert any volumes into dm3. (cm3 --> dm3 = x10-3 ) n(NaOH) = 0.025x0.1 = 0.0025Then use the n=cV equation to work out the concentration of HCl. Remember that since they react in a 1:1 ratio, the number of moles of HCl is equal to the number of moles of NaOH. n=cV so c=n/V c=0.0025/0.015 = 0.16666...moldm-3
