An organic compound contains 60% carbon, 13.3% hydrogen and 26.7% oxygen. Calculate the empirical formularn(C=12,H =1, O=16)

To find the empirical formula of this organic compound, we need to determine the simplest whole-number ratio of the atoms present. We follow these steps:

1. Analyze the composition

• Carbon (C): 60%
• Hydrogen (H): 13.3%
• Oxygen (O): 26.7%

2. Calculate the number of moles

Assume we have 100g of the compound. This means we have 60g of C, 13.3g of H, and 26.7g of O. We divide the mass of each element by its relative atomic mass (C=12, H=1, O=16):

• Moles of C: $\frac{60}{12} = 5.0$
• Moles of H: $\frac{13.3}{1} = 13.3$
• Moles of O: $\frac{26.7}{16} = 1.67$

3. Divide by the smallest value

To get the simplest ratio, divide each result by the smallest number of moles calculated (which is 1.67):

• Ratio of C: $\frac{5.0}{1.67} \approx 3$
• Ratio of H: $\frac{13.3}{1.67} \approx 8$
• Ratio of O: $\frac{1.67}{1.67} = 1$

4. Determine the Empirical Formula

The ratio of C : H : O is 3 : 8 : 1. Therefore, the empirical formula is $C_3H_8O$.

Comparing this to your options: A. $C_5H_{12}O$ B. $C_3H_8O$ C. $C_6H_{13}O_2$ D. $C_4H_9O$

The calculated formula matches option B.

Exam Tip: When calculating empirical formulas, if your division results in a decimal like 0.5, multiply all values by 2 to get a whole number. If you get 0.33, multiply by 3. In this case, the values were very close to whole numbers, making the calculation straightforward.