How many grams of concentrated nitric acid solution should be used to prepare 250 mL of 2.0 M `HNO_(3)` solution ? The concentration of nitric acid is 70 % by mass.

Options

A. 54.0 g conc. `HNO_(3)`
B. 45.0 g conc. `HNO_(3)`
C. 90.0 g conc. `HNO_(3)`
D. 70.0 g conc. `HNO_(3)`

Answer

B

Explanation

Molarity `= ("Mass of HNO"_(3))/("Molar mass " xx " volume of solution in L")`
`("2.0 mol L"^(-1))=(W)/(("63 g mol"^(-1))xx("0.250 L"))`
`W=("2.0 mol L"^(-1))xx("63 g mol"^(-1))xx("0.250 L")`
`=31.5g`
Actual mass of `HNO_(3)=31.5gxx(70)/(100)=45.0g`.