Volume of NaOH = 20 mL / 1000 = 0.02 L
Molarity NaOH = 4.0 M
number of moles NaOH :
n = M * V
n = 4.0 * 0.02
n = 0.08 moles of NaOH:
Finally we calculate the number of moles of HCl in the solution from the stoichiometry of the reaction :
HCl + NaOH = NaCl + H₂O
1 mole HCl ---------- 1 mole NaOH
? moles HCl --------- 0.08 moles NaOH
moles HCl = 0.08 * 1 / 1
= 0.08 moles of HCl
Volume of HCl = 20 mL / 1000 = 0.02 L
M ( HCl ) = n / V
M = 0.08 / 0.02
= 4.0 M
hope this helps!
