Question

A metal oxide (MO) is reduced by heating it in a stream of hydrogen. It is found that after complete reduction, 7.95 g of oxide requires $0.2gof{H}_2$ to yield 6.35 g of the metal. We may deduce that:

• A. the atomic weight of the metal is 48.
• B. the atomic weight of the metal is 16.
• C. the atomic weight of the metal is 12.
• D. the atomic weight of the metal is 63.5.

Answer 1

The correct option is D the atomic weight of the metal is 63.5.

The balanced equation can be written as:
$MO+H_2\to M+H_{2}O$
1 mole of MO requires = 1 mole of $H_2$
Now 0.2g of $H_2$ = 0.1 mole of $H_2$
$\therefore$ For 0.1 mole of $H_2$ = 0.1 mole of MO = 7.95g of MO is required
If 0.1mole of MO = 7.95g
1 mole of MO = 79.5g
Weight of MO = M + 16
$\therefore$ Atomic weight of metal(M) = 79.5 - 16 =$63.5g$