Question

How many grams of concentrated nitric acid solution should be used to prepare 250mL of 2.0M HNO3 ?The concentrated acid is 70% HNO3.

Answer 1

The required number of moles=( 250/1000)×2
=0.5 moles
(no. of moles=molarity × volume)
so,required mass of HNO3=0.5×63
=31.5 grams
(given mass=no. of moles × molar mass)
Given,
70 grams of HNO3 are present in 100 grams of the solution
so,1 gram will be present in 100/70 grams of solution
hence 31.5 grams will be present in (100/70)×31.5 grams of solution.
so amount of concentrated nitric acid solution used is 45 grams.

Answer 2

Answer:

The concentrated nitric acid solution needed to prepare the given solution is 45grams.

Explanation:

Moalrity of solution = (no. of moles/volume of solution) ×1000

No.of moles nitric acid= (Molarity×volume)/1000

= (2M×250ml)/1000= 0.5 mol

mass=no. of moles× molar mass

mass of nitric acid= (0.5)(63)=31.5grams

Given that

70g of nitric acid present= 100g of solution

31.5g of nitric acid present=

$= 31.5 \times \frac{100}{70 } = 45grams$

Therefore 45grams of concentrated nitric acid solution is required.