10 ml of a solution of NaOH is found to be completely neutralised by 8ml of a given solution of HCl. If we take 20 ml of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be : (a) 4 ml (b) 8ml (c) 12 ml 16ml

Option (d) is the answer. It is given that 10ml of a solution of NaOH is completely neutralised by 8ml of a solution of HCl. Then 20ml of the solution of NaOH which is double the amount taken before will require double the solution of HCl taken earlier. That is 16ml to be completely neutralised.