Question

The mass of magnesium oxide formed by burning $1.216g$ magnesium in excess oxygen is:

• A. $0.416g$
• B. $1.616g$
• C. $2.016g$
• D. $2.816g$

Answer 1

The correct option is C $2.016g$

No.of moles of $Mg$ $=\frac{givenmass}{atomicmass}$

$=\frac{1.216}{24}$

$=0.05$
Now the balanced equation for the reaction is:
$2Mg+O_2\to 2MgO$
$0.05$ moles of magnesium will form $0.05$ moles of magnesium oxide($MgO$).
$\therefore$ mass of $0.05$ moles of $MgO$ $=0.05\times 40$

$=2.016g$