A sample of a substance (containing only C, H, and N) is burned in oxygen.
7.961 g of CO2, 1.164 g of H2O and 1.551 g of NO are the sole products of combustion.
What is the empirical formula of the compound?
mols C = 7.961/44 = ?
mols H = 1.164 x (2/18) = ?
mols N = 1.551/30 = ?
Now find the ratio in small whole numbers to one another. The easy way to do that is to divide the smallest number by itself (which gives you 1.000), then divide the other numbers by the same small number. Round to whole number to find CxHyNz. Post your work if you have trouble.
To determine the empirical formula of the compound, we need to find the ratio of the elements present in the sample.
First, let's calculate the number of moles for each product:
1. Moles of CO2:
- Molar mass of CO2 = (12.01 g/mol) + 2(16.00 g/mol) = 44.01 g/mol
- Moles of CO2 = mass of CO2 / molar mass of CO2
= 7.961 g / 44.01 g/mol
≈ 0.181 mol
2. Moles of H2O:
- Molar mass of H2O = 2(1.01 g/mol) + 16.00 g/mol = 18.02 g/mol
- Moles of H2O = mass of H2O / molar mass of H2O
= 1.164 g / 18.02 g/mol
≈ 0.065 mol
3. Moles of NO:
- Molar mass of NO = 14.01 g/mol + 16.00 g/mol = 30.01 g/mol
- Moles of NO = mass of NO / molar mass of NO
= 1.551 g / 30.01 g/mol
≈ 0.052 mol
Next, we need to find the ratio of the moles of each element. Divide the number of moles of each element by the smallest number of moles obtained (in this case, the moles of NO):
- Carbon (C): 0.052 mol / 0.052 mol = 1
- Hydrogen (H): 0.065 mol / 0.052 mol ≈ 1.25
- Nitrogen (N): 0.052 mol / 0.052 mol = 1
Now, we need to simplify the ratio by dividing each value by the lowest whole-number ratio. Rounded to the nearest whole number, we have:
- Carbon (C): 1
- Hydrogen (H): 1.25 ≈ 1
- Nitrogen (N): 1
Therefore, the empirical formula of the compound is CHN.