Question

A metal oxide has the formula $Z_2{O}_3$. It can be reduced by hydrogen to give free metal and water. 0.1596 g of the metal requires 6 mg of hydrogen for complete reduction. The atomic mass of the metal is:

• A. 27.9 g $mo{l}^{-1}$
• B. 159.6 g $mo{l}^{-1}$
• C. 79.8 g $mo{l}^{-1}$
• D. 55.8 g $mo{l}^{-1}$

Answer 1

The correct option is C 79.8 g $mo{l}^{-1}$

$Z_2{O}_3+3H_2\left(g\right)\to 2Z+3H_{2}O$

$\therefore 6g{H}_2$ gives mole Z

$\therefore 6\times {10}^{-3}g{H}_2$ will give $0.002$ mole $Z$

Number of moles $=\frac{Mass}{Molarmass}$

$0.002=\frac{0.1596}{Molarmass}$

$\therefore$ Molar mass $=\frac{0.1596}{0.002}=79.8gmo{l}^{-1}$