Q. 7.12 - An Introduction to General, Organic, and Biological Chemistry

Question

Calculate the molar mass for each of the following : 

a. ${\mathrm{O}}_2$      b. ${\mathrm{KH}}_2{\mathrm{PO}}_4$     c. $\mathrm{Fe}{\left({\mathrm{ClO}}_4\right)}_3$

Step-by-Step Solution

Answer

a. The molar mass of ${\mathrm{O}}_2$ is $31.98 \mathrm{g}$

b. The molar mass of ${\mathrm{KH}}_2{\mathrm{PO}}_4$ is $136.02 \mathrm{g}$

c. The molar mass of $\mathrm{Fe}{\left({\mathrm{ClO}}_4\right)}_3$ is $354.07 \mathrm{g}$

Part (a) Step 1 : Given information

We have to calculate the molar mass of  ${\mathrm{O}}_2$

Part (a) Step 2 : Simplification

We know that,

Molar mass of one $\mathrm{O}$ atom = $15.99 \mathrm{g}$

So, molar mass of ${\mathrm{O}}_2$( two $\mathrm{O}$ atoms ) =$2\left(15.99\right)$ = $31.98 \mathrm{g}$

Part (b) Step 1 : Given information

We have to calculate the molar mass of  ${\mathrm{KH}}_2{\mathrm{PO}}_4$

Part (b) Step 2 : Simplification

We know that,

Molar mass of one $\mathrm{K}$ atom = $39.09 \mathrm{g}$

Molar mass of one $\mathrm{H}$ atom = $1.00 \mathrm{g}$

Molar mass of one $\mathrm{P}$ atom = $30.97 \mathrm{g}$

Molar mass of one $\mathrm{O}$ atom = $15.99 \mathrm{g}$

So, molar mass of ${\mathrm{KH}}_2{\mathrm{PO}}_4$ = $39.09 + 2\left(1.00\right) + 30.97 + 4\left(15.99\right)$ = $136.02 \mathrm{g}$

Part (c) Step 1 : Given information

We have to calculate the molar mass of  $\mathrm{Fe}{\left({\mathrm{ClO}}_4\right)}_3$

Part (c) Step 2 : Simplification

We know that,

Molar mass of one $\mathrm{Fe}$ atom = $55.84 \mathrm{g}$

Molar mass of one $\mathrm{O}$ atom = $15.99 \mathrm{g}$

Molar mass of one $\mathrm{Cl}$ atom = $35.45 \mathrm{g}$

So, molar mass of $\mathrm{Fe}{\left({\mathrm{ClO}}_4\right)}_3$=$55.84 + 3\left(35.45\right) + 12\left(15.99\right)$ = $354.07 \mathrm{g}$