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


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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}=(71.0g)/(63.01g/mol)=1.13moles`

Thus there are 1.13 moles of
`HNO_3`