Some Basic Concepts Of Chemistry

Question

Commercially available concentrated hydrochloric acid contains 38% HCl by mass.
(i) What is the molarity of the solution (density of solution = 1·19g cm^-3)?
(ii) What volume of concentrated HCl is required to make 1·0L of 0·10 M HCl?

Solution

(i) 38% HCl by mass means that 38g of HCl is present in 100g of solution.
Volume of solution

equals space fraction numerator Mass space over denominator Density end fraction space equals space fraction numerator 100 over denominator 1.19 end fraction space equals 84.03 space cm cubed

Moles of HCl =

fraction numerator 38 over denominator 36.5 end fraction space equals space 1.04

Molarity =

fraction numerator No. space of space moles space of space HCl over denominator Vol. space of space solution space left parenthesis in space cm cubed right parenthesis end fraction cross times 100

equals space fraction numerator 1.04 over denominator 84.03 end fraction cross times 1000 space equals space 12.38 space straight M

(ii) By applying normality equation,

straight M subscript 1 straight V subscript 1 space equals space straight M subscript 2 straight V subscript 2 comma space we space have

12.38 space straight M space cross times space straight V subscript 1 space equals space 0.10 space cross times space 1.0 space straight L therefore space space space space space straight V subscript 1 space equals space fraction numerator 0.10 space cross times space 1.0 over denominator 12.38 end fraction space space space space space space space space space space space space space equals space 0.00808 straight L space space space space space space space space space space space space space equals space 8.08 space cm cubed

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