Question

How many grams of HNO3 is required to prepare 400ml solution of 0.2M HNO3 ?

Answer 1

Molar mass of HNO3 = 1+14+16x3 = 63g/mol

0.2M means 0.2 moles in 1000ml

∴ 400ml will contain = 400/1000 x 0.2 = 0.08 moles

Mass of HNO3 = Molar mass x no. of moles
                         = 63 x 0.08 = 5.04g

Answer 2

5.04 g of HNO3 is required to prepare 0.2 M 400 mL of HNO3 solution.

Given,

Molarity of the solution=0.2 M

Volume of the solution=400 mL.

To find,

the mass of HNO3 required to prepare 0.2 M HNO3 solution.

Solution:

• Molarity of a substance in a solution is defined as the moles of that substance in 1 L of solution.
• $Molarity=\frac{Moles}{Volume(L)} .$
• Molarity is a temperature dependent concentration term.

Moles of HNO3 present in the solution are:

$Molarity=\frac{Moles}{Volume(L)} \\0.2=\frac{Moles}{\frac{400}{1000} } \\0.2=\frac{Moles}{0.4} \\Moles=0.4X0.2\\Moles=0.08.$

0.08 moles of HNO3 are present in the solution.

The molar mass of HNO3 is 63 g.

0.08 moles of HNO3 will have a mass of:

$Moles=\frac{Mass}{Molar mass} \\0.08=\frac{Mass}{63}\\Mass=0.08X63\\Mass=5.04 g.$

0.08 moles of HNO3 will have a mass of 5.04 g.

Thus, the mass of HNO3 required is 5.04 g.

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