Q.32E - Chemistry (OpenStax)

Question

Determine the empirical formulas for the following compounds.

a. acetic acid, C₂H₄O₂

b. citric acid, C₆H₈O₇ 

c. hydrazine, N₂H₄ 

d. nicotine, C₁₀H₁₄N₂

e. butane, C₄H₁₀

Step-by-Step Solution

Answer

The empirical formulas for the respective compounds are given below:

1. CH₂O
2. C₆H₈O₇
3. NH₂
4. C₅H₇N₁
5. C₂H₅

Step 1: Definition of empirical formula

When atoms in a chemical compound are expressed in the simplest ratio, it is known as the empirical formula.

 

For example, the empirical formula for glucose (C₆H₁₂O₆) will be CH₂O.

Step 2: Determining the empirical formula of acetic acid.

The formula of acetic acid is C₂H₄O₂, that the conversion of 2,4 and 2 into their simple whole-number ratio will result in 1,2,1. Hence, the empirical formula for acetic acid is CH₂O.

Step 3: Determining the empirical formula of citric acid

The formula of acetic acid is C₆H₈O₇ since there is no lowest common factor between 6,8 and 7. Hence, the empirical formula for citric acid is C₆H₈O₇. 

Step 4: Determining the empirical formula of hydrazine

The formula for hydrazine is N₂H₄. The lowest common factor of 2 and 4 is 2. Dividing 2 and 4 by 2 will result in 1 and 2. Hence, the empirical formula of hydrazine is NH₂

Step 5: Determination of empirical formula of nicotine

The formula for nicotine is C₁₀H₁₄N₂, that the lowest common factor for 10,14, and 2 is 2. Divide all the numerical values by 2. Hence the simplest ratio will be 5,7 and 1. Hence, the empirical formula for nicotine is C₅H₇N

Step 6: Determining empirical formula for butane

The formula for butane is C₄H₁₀. The lowest common factor for 4 and 10 is 2. Divide 4 and 10 by 2. Thus, the simplest whole-number ratio will be 2 and 5. Thus, the empirical formula for butane is C₂H₅.