Question

A nitric acid solution containing 71.0% HNO3 (by mass) is available in a laboratory. How many moles of HNO3 are present in 1.98 L of this solution?
 

a. 

62.8 mol

 

b. 

31.7 mol

 

c. 

22.3 mol

 

d. 

 0.0316 mol

 

e. 

none of these


​

Answer 1

Answer:   e. none of these

Explanation:

Mass percent is the ratio of mass of solute dissolved to the mass of solution in terms of percentage.

Thus 71.0% $HNO_3$ means 71.0 g of $HNO_3$ is present in 100 g of solution  

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

given mass of $HNO_3$  = 71.0 g

Molar mass of  $HNO_3$ = 63.01 g/mol

Putting in the values we get:

$\text{Number of moles}=\frac{71.0g}{63.01g/mol}=1.13moles$

Thus there are 1.13 moles of $HNO_3$