85 cm^3 of 0.05 mol/dm^3 sulfuric acid is used to neutralise 15 cm^3 of sodium hydroxide of an unknown concentration. Given that the chemical formula of the reaction is 2NaOH + H2SO4 => NA2SO4 + 2H2O, find the concentration of the sodium hydroxide.
Firstly, calculate the number of moles of sulfuric acid that reacts with the sodium hydroxide, using the equation; n = MV/1000 , where n is the number of moles, M is the concentration (in mol/dm3), and V is the volume (in cm3). n = (0.05 x 85)/1000 = 0.00425 mol. Looking at the equation for the neutralisation reaction; 2NaOH + H2SO4 => NA2SO4 + 2H2O , it can be seen that 1 mol of sulfuric acid reacts with 2 mol of sodium hydroxide. Therefore, the number of moles of sodium hydroxide in the solution is 2 x 0.00425 = 0.0085. Rearranging the previous equation to be able to find the concentration; M = 1000n/V , Therefore the concentration of sodium hydroxide can be found; (1000 x 0.0085)/15 = 0.566666 = 0.567 mol/dm3
