Question

what is the empirical formula of a compound composed of 24.9 g of K and 5.09 g of O

Answer 1

Empirical formula- Empirical formula is the reduced form of molecular formula which does not tell us exactly the number of each atoms present but gives us a ratio of the elements.

To find the empirical formula, we need to find the no of moles first.

Calculating the no. of moles is done by using the formula,

No. of moles (N) = Given mass in grams / Molar mass in gram per mol

Thus the no. of moles of potassium,

N_k = 24.9 g / 39.0983 g mol^-1

N_k = 0.63685 mol

No. of moles of Oxygen-

N_O = 5.09 g / 16 g mol^-1

N_O = 0.318125 mol

Now we check which element has the lowest number of moles and divide all the moles with that number-

here the smallest number is 0.318125 mol

Thus, N_k / N_O = 2.001

  N_O / N_k  = 1.00

The Ratio is 2:1

The Empirical formula is K₂O