21.65 cm3 of hydrochloric acid was used to completely neutralize 25 cm3 of sodium hydroxide of concentration 0.2mol dm-3. calculate the concentration of hydrochloric acid.

Answers 1

Answer:

The reaction is: HCl + NaOH to NaCl + H2O. Calculate the concentration of the hydrochloric acid.

using the equation n = cv (number of moles = concentration x volume).

To do this we need to convert the volume 28.60 cm3 into dm3 (which is the same as litres). There are 1000 cm3 in a dm3 so

28.60 cm3 = 28.60 / 1000 dm3 = 0.0286 dm3

Now we can use n = cv = 0.200 moles per dm3 x 0.0286 dm3 = 0.00572 moles of sodium hydroxide

Since one mole of hydrochloric acid reacts with one mole of sodium hydroxide, 0.00572 moles of hydrochloric acid reacted.

We can now use the equation n=cv and rearrange it to c = n/v to find the concentration of hydrochloric acid.

The volume of hydrochloric acid again needs converting to dm3:

25.00 cm3 = 25.00/1000 dm3 = 0.025 dm3

c = n/v = 0.00572 moles / 0.025 dm3 = 0.23 moles per dm3