Q84P - Chemistry: Molecular Nature Of Matter And Change

Question

Write an empirical formula for each of the following:

(a) Hydrazine, a rocket fuel, molecular formula ${\mathbf{N}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{4}}$

(b) Glucose, a sugar, molecular formula ${\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}$

Step-by-Step Solution

Answer

(a) The empirical formula for Hydrazine is ${\mathbf{NH}}_{\mathbf{2}}$ .

(b) The empirical formula for glucose is ${\mathbf{CH}}_{\mathbf{2}}\mathbf{O}$.

Step 1:Definition of empirical formula

A chemical formula that gives the simplest ratio of elements present in a

compound but not the actual numbers of atoms is known as the empirical formula.

Step 2: Empirical formula for Hydrazine

Hydrazine,${\mathbf{N}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{4}}$, contains nitrogen and hydrogen.

The ratio of nitrogen to hydrogen is 1:2.

So, ${\mathbf{NH}}_{\mathbf{2}}$ is the empirical formula for Hydrazine.

Step 3: Empirical formula for glucose

Glucose,${\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}$ , contains carbon, hydrogen and oxygen. 

We have to check the ratio of different elements to find out the empirical formula.

 $$\begin{gathered} {\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{6}}\mathbf{:}\mathbf{C}\mathbf{:}\mathbf{H}\mathbf{:}\mathbf{O}\mathbf{:}\mathbf{:}\mathbf{6}\mathbf{:}\mathbf{12}\mathbf{:}\mathbf{6} \\ \mathbf{simplestratio}\mathbf{,}\mathbf{C}\mathbf{:}\mathbf{H}\mathbf{:}\mathbf{O}\mathbf{:}\mathbf{:}\mathbf{1}\mathbf{:}\mathbf{2}\mathbf{:}\mathbf{1} \end{gathered}$$

 So, ${\mathbf{CH}}_{\mathbf{2}}\mathbf{O}$is the empirical formula for glucose.