Question

$2Mg+O_2\to 2MgO$
Use the equation above to answer the following question.
If $0.486g$ of magnesium and $6.022\times {10}^{20}$ molecules of oxygen react, what mass of magnesium oxide will be formed?

• A. $0.646g$
• B. $0.806g$
• C. $0.24g$
• D. $0.08g$

Answer 1

The correct option is D $0.08g$

$2Mg+O_2\to 2MgO$

Molar mass of Mg $=24g$

Molar mass of MgO $=40g$

No. of moles of $O_2=\frac{6.022\times {10}^{20}}{6.022\times {10}^{23}}=0.001\text{mole of}{O}_2$

No. of moles of Mg$=\frac{0.486}{24}=0.02\text{moles}$ of Mg

As moles of $O_2$ are less than $0.01,O_2$ is limiting reagent and $0.002moles$ of MgO is formed.

$\Rightarrow 0.002\times 40=0.08g$ of MgO