Question

0.242 g sample of K is heated in the presence of oxygen gas. This resulted in the formation of 0.440 g of a crystalline compound. What is the formula of this compound?

• A. $KO$
• B. $K_{2}O$
• C. $K{O}_2$
• D. $K{O}_3$

Answer 1

The correct option is C $K{O}_2$

$xK+y{O}_2\to product$
Amount of $O_2$ used = 0.440 - 0.242 = 0.198g
Moles of $O_2$ = $\frac{0.198}{32}\cong 6.2\times {10}^{-3}$
Moles of $K$ = $\frac{0.242}{39}\cong 6.2\times {10}^{-3}$
Hence, it can be concluded that 1 mol of K reacts with 1 mol of oxygen and the formula of the product is $K{O}_2$.