Question

Preparation of a buffer:
Dissolve in a beaker 27.3 g NaC2H3O2·3H2O in water containing 60 mL of 1 M HCl (you need to make a 250- mL of 1 M hydrochloric acid solution in advance by the appropriate dilution of concentrated HCl) and dilute with the distilled water to 1 L. Invert the bottle up to 20 times and keep the buffer in a 1 L glass bottle.

*help with dilution of concentrated hcl

Answer 1

Ans. Concentrated HCl available for laboratory use is around 11 N, the packaging must be labelled indicating the strength. If not the strength of a HCs solution can be calculated using its specific gravity, % amount and % purity.

It’s assumed that the concentrated HCl available in the laboratory is of 11 normality (11 N, standard strength of concentrated HCl).

Suppose, you require 1 L (= 1000 mL) of 1 N HCl.

Now, Using, M1V1 = M2V2        , where

C1= concentration of original HCl solution 1, V1= volume of original HCl solution 1      ;(11 N)

C2= concentration of final solution 2, V2= volume of final solution 2        ; [1N, you need to prepare]

11 N x V1 = 1 N x 1000 mL

Or, V1 = (1 N x 1000 mL) / 11 N = 90.90 mL

That is, transfer 90.90 mL of concentrated HCl (11 N) to 1 L (= 1000 mL) standard volumetric flask and make the volume upto the mark with distilled water. It is 1 L of 1 N HCl.

Note: It is always advising that you first fill the volumetric flask (around 1/3^rd volume) with distilled water and place it on cool pack or ice bath. Gradually add (in small volume at a time) concentrated HCl to the sides of the wall of the flask with careful swirling. After you add 90.90 mL of concentrated HCL to the flask, add distilled water so that the volume still remains below the mark (say, around 2 inches below the mark). Allow the flask to attain room temperature. Once room temperature is attained, add distilled water carefully to make the volume upto the mark. It’s your final 1N HCl solution, volume 1 L.