Question

1. a compound contains an unknown element x. this element forms an oxide with chemical formula x₂o. experimental tests show that x₂o contains 25.8% oxygen, by mass. t/i (a) what is the percentage of element x in the compound? (b) use this information to identify element x.

Explanation:

Step1: Calculate the percentage of element X

The total mass percentage of a compound is \(100\%\). Given that oxygen is \(25.8\%\) by mass.

$$ \text{Percentage of }X=100\% - 25.8\% $$

Step2: Solve for the percentage of X

$$ \text{Percentage of }X = 74.2\% $$

Step3: Let the atomic mass of \(X\) be \(M\).

The molar mass of \(X_{2}O\) is \(2M + 16\) (since the atomic mass of \(O\) is \(16\ g/mol\)).
We know that \(\frac{16}{2M + 16}=0.258\) (because the mass percentage of \(O\) is \(25.8\%\) or \(0.258\))

$$ 16=0.258\times(2M + 16) $$

$$ 16 = 0.516M+4.128 $$

$$ 0.516M=16 - 4.128 $$

$$ 0.516M = 11.872 $$

$$ M=\frac{11.872}{0.516}\approx23\ g/mol $$

Answer:

a. \(74.2\%\)
b. Sodium (\(Na\)) (since the atomic mass of \(Na\) is approximately \(23\ g/mol\))