Question

Binary compound of oxygen and an unknown element,X, has the formula XO2 and is 69.55 mass % oxygen, what is the weight of element X?

Answer 1

Answer:

Weight of element X = 14.01 gram

Explanation:

Mass percentage is calculated by using :

$Percent =\frac{Mass\ of\ element}{Total\ mass}\times 100$

$O\ Percent=\frac{Mass\ of\ O}{Total\ mass\ of\ XO2}\times 100$

Mass of O = 16.0 gram

let mass of X = X grams = ?

Mass of XO2 = mass of X + 2(mass of O)

Mass of XO2 = X + 2(16)

Mass of XO2 = X + 32

Total mass of O in the compound = 2(16) = 32 grams

Percent O = 69.55 %

$Percent\ O =\frac{Mass\ of\ O}{Total\ mass\ of\ XO2}\times 100$

$69.55=\frac{32}{X+32}\times 100$

$\frac{69.55}{100}=\frac{32}{X+32}$

$0.6955=\frac{32}{X+32}$

$0.6955\times (X+32)=32$

$0.6955X+ 22.256=32$

$0.6955X=9.744$

$X=\frac{9.744}{0.6955}$

$X =14.01$

weight of element X = 14.01 gram

14.01 is mass of nitrogen N

The correct formula of this element is NO2