Question 1
A compound is composed of 13% carbon, 4.3% hydrogen, 30.4% nitrogen, and 52.2% oxygen. The mystery compound has a molar mass of 184 grams per mole. What is the molecular formula of the compound?
Explanation: When finding molecular formulas, imagine a 100-gram sample of the compound. We can then use the percentages of each atom and convert them to grams.
The next step is to divide the given mass of each atom by its atomic mass. This will give you four separate molar values that you can compare to one another.
Next, you must divide each molar value by the smallest of the values. This will result in the molar ratios of each compound. In this case, carbon has the lowest molar value at 1.08. After dividing all four numbers by this value, we determine a molar ratio of 1:4:2:3 for carbon, hydrogen, nitrogen, and oxygen, respectively.
At this point, we have determined the empirical formula for the compound, however, we need to find the formula that gives a molar mass of 184 grams per mole. Start by calculating the molar mass of the empirical formula.
Since the empirical formula has a molar mass of 92 grams per mole, we need to multiply the empirical formula by 2.
This results in a molecular formula of 
.
The next step is to divide the given mass of each atom by its atomic mass. This will give you four separate molar values that you can compare to one another.
Next, you must divide each molar value by the smallest of the values. This will result in the molar ratios of each compound. In this case, carbon has the lowest molar value at 1.08. After dividing all four numbers by this value, we determine a molar ratio of 1:4:2:3 for carbon, hydrogen, nitrogen, and oxygen, respectively.
At this point, we have determined the empirical formula for the compound, however, we need to find the formula that gives a molar mass of 184 grams per mole. Start by calculating the molar mass of the empirical formula.
Since the empirical formula has a molar mass of 92 grams per mole, we need to multiply the empirical formula by 2.
This results in a molecular formula of .