Question

How many grams of sulphuric acid is to be dissolved to prepare $200 \,mL$ aqueous solution having concentration of $[H_{3}O^{+}]$ ions $1 \,M$ at $25^{\circ}C$ temperature?

• A. $4.9 \,g$
• B. $19.6 \,g$
• C. $9.8 \,g$
• D. $0.98 \,g$

Answer 1

Answer: (C)

$9.8 \,g$

Answer 2

Two $[H_3O^+]$ ions are obtained from $1 \,M \,H_2SO_4$. $\therefore$ One $[H_3O^+]$ ion is obtained from $0.5 \,M \,H_2SO_4$. Molarity $=\frac{m\left(H_{2}SO_{4}\right) \times 1000}{M\left(\text{molar mass} H_{2}SO_{4}\right) }\times \text{volume of solution} (mL)$ $0.5=\frac{m \times 1000}{98 \times200}$ $m=\frac{0.5 \times 98 \times200}{1000}$ $=9.8\,g$