Question

measurements show that unknown compound x has the following composition: element mass % nitrogen 26.0% oxygen 74.1% write the empirical chemical formula of x.

Explanation:

Step1: Assume 100g of the compound

Since we have mass - percentages, assuming 100g of the compound means we have 26.0g of nitrogen (N) and 74.1g of oxygen (O).

Step2: Calculate the number of moles of each element

The molar mass of N is approximately 14.01 g/mol, and the molar mass of O is approximately 16.00 g/mol.
The number of moles of N, $n_N=\frac{26.0g}{14.01g/mol}\approx1.856mol$.
The number of moles of O, $n_O=\frac{74.1g}{16.00g/mol}\approx4.631mol$.

Step3: Find the mole - ratio of the elements

Divide each number of moles by the smaller number of moles. Here, the smaller number of moles is $n_N = 1.856mol$.
The ratio of N to O is $\frac{n_N}{n_N}:\frac{n_O}{n_N}=\frac{1.856mol}{1.856mol}:\frac{4.631mol}{1.856mol}\approx1:2.5$.
Since we need whole - number ratios, multiply each by 2 to get 2:5.

Answer:

$N_2O_5$