What is pH of an aqueous solution formed by adding 20 mL of 0.1 mol L-1 NaOH to 30 mL of 0.2 mol L-1 HCI?

Please show steps and maths. Is there a unit conversion if so how is this done.

Thank you

1 answer

HCl + NaOH ==> NaCl + H2O
moles HCl initially = M x L = ??
moles NaOH initially = M x L = ??
Since these react, one of them will be used completely and the other will have some remaining. What you do is subtract the smaller moles of reagent from the larger moles of reagent, then use the excess of the remaining solution (still in moles) to convert to M (M = moles/L), then to pH.