Question

What volume of $0.1MBa(OH{)}_2$ will be required to neutralize a mixture of $50$ mL of $0.1MHCl$ and $100$ mL of $0.2M{H}_{3}P{O}_4$ using methyl red indicator?

• A. $25$ mL
• B. $50$ mL
• C. $100$ mL
• D. $125$ mL

Answer 1

Answer: (D)

$125$ mL

Methyl red indicates complete ionization of $HCl(n=1)$ and first step ionization of $H_{3}P{O}_4(n=1)$.
First case:
$Ba(OH{)}_2\equiv HCl$
$0.1\times 2\times V_1=0.1\times 1\times 50$
$V_1=25$ mL
Second case:
$Ba(OH{)}_2\equiv H_{3}P{O}_4(n=1)$
$0.1\times 2\times V_1=0.2\times 1\times 100$

$V_1=100$ mL
Total volume $=100+25=125$ mL