Answer :
Answer:
90 mL
Explanation:
Step 1:
Data obtained from the question. This include the following:
Volume of base, NaOH (Vb) =..?
Molarity of base, NaOH (Mb) = 0.1 M
Volume of acid, H3PO4 (Va) = 15 mL
Molarity of acid, H3PO4 (Ma) = 0.2 M
Step 2:
The balanced equation for the reaction. This is given below:
H3PO4 + 3NaOH —> Na3PO4 + 3H2O
From the balanced equation above,
Mole ratio of the acid, H3PO4 (nA) = 1
Mole ratio of base, NaOH (nB) = 3
Step 3:
Determination of the volume of the base. The volume of the base needed for the reaction can be obtained as follow:
MaVa / MbVb = nA/nB
0.2 x 15 / 0.1 x Vb = 1/3
Cross multiply
0.1 x Vb = 0.2 x 15 x 3
Divide both side by 0.1
Vb = (0.2 x 15 x 3) / 0.1
Vb = 90 mL
Therefore, 90 mL of the base, NaOH is needed for the reaction.