Question

A sample of a white powder contains 40 g of carbon, 6.67 g of hydrogen, and 53.33 g of oxygen. What is the empirical formula of this compound?

Answer 1

To calculate the empirical formula, divide the mass of each element by its atomic mass to get moles, normalize the ratio by dividing by the smallest number of moles, and express it as the simplest whole number ratio. For this sample, the empirical formula is CH₂O.

Step-by-step explanation:

To determine the empirical formula of a compound, we calculate the moles of each element present and then find the simplest whole number ratio of these elements. Let's use the sample containing 40 g of carbon (C), 6.67 g of hydrogen (H), and 53.33 g of oxygen (O).

• First, we divide the mass of each element by its atomic mass to get the number of moles:
  C: 40 g / 12.01 g/mol = 3.33 mol
  H: 6.67 g / 1.008 g/mol = 6.61 mol
  O: 53.33 g / 16.00 g/mol = 3.33 mol
  
• Then, we divide each of these amounts by the smallest number of moles to normalize the ratio:
  C: 3.33 / 3.33 = 1
  H: 6.61 / 3.33 = 1.99, which we round to 2
  O: 3.33 / 3.33 = 1
  
• The resulting ratio is 1 carbon to 2 hydrogens to 1 oxygen.
  
• Thus, the empirical formula of the compound is CH₂O.

Remember, the empirical formula represents the simplest whole-number ratio of elements in a compound.