Answer:
Option B. 20mL
Explanation:
Step 1:
Data obtained from the question.
Volume of base (Vb) =..?
Molarity of base (Mb) = 0.2M
Volume of acid (Va) = 40mL
Molarity of acid (Ma) = 0.1M
Step 2:
The balanced equation for the reaction.
HCl + NaOH —> NaCl + H2O
From the balanced equation above, the following were obtained:
Mole ratio of the acid (nA) = 1
Mole ratio of the base (nB) = 1
Step 3:
Determination of the volume of base, NaOH needed for the reaction. This is illustrated below:
MaVa/MbVb = nA/nB
0.1 x 40 / 0.2 x Vb = 1
Cross multiply
0.2 x Vb = 0.1 x 40
Divide both side by 0.2
Vb = 0.1 x 40 / 0.2
Vb = 20mL
Therefore, the volume of the base is 20mL.
