Preparation Of Chemical SolutionsHow to determine the molarity of Commercial Concentration ReagentsFor example the label on a bottle of commercial sulphuric acid is : Specific Gravity = 1.84 Percentage = 96

Determine the molarity of H2SO4 .

Solution:Density of H2SO4 = 1.84g / 1mlRelative molecular mass in grams = 98gWeight of H2SO4 in 1ml = 1.84g / 1ml x 96/100 = 1.77gWeight of H2SO4 in 1l = 1.77g / 1ml x 1000ml/1l = 1770g/lMolarity of H2SO4 = 1770 / 98 = 18 M

Activity: Determine the molarity of hydrochloric acid if the specific gravity is 1.18 and the percentage is 36.

Solution:Density of HCl = 1.18g / 1mlRelative molecular mass in grams = 36.5gWeight of HCl in 1ml = 1.18g / 1ml x 36/100 = 0.425gWeight of HCl in 1l = 0.425g / 1ml x 1000ml/1l = 425g/lMolarity of HCl = 425 / 36.5 = 11.6M

Preparation of Stock Solution Stock solutions are usually prepared from commercial concentrations by using this formula:

M1V1 = M2V2

M1 = Molarity of concentrated solutionV1 = Volume of concentrated solutionM2= Molarity of dilute solutionV2 = Volume of dilute solution

ExampleA dilute solution of sulphuric acid is to be prepared from concentrated solution. How many ml of 18M H2SO4 is required to make 120ml 3M H2SO4 ?

Solution:M1= 18M ; V1=? ; M2 = 3M ; V2 = 120ml

V1 = M2V2 = 3 x 120 = 20ml M1 18

Activity:If you have stock solution of 2M hydrochloric acid, explain how you can prepared 500ml 0.1M hydrochloric acid from the stock solution.

Solution:M1= 2.0M ; V1=? ; M2 = 0.1M ; V2 = 500ml

V1 = M2V2 = 0.1 x 500 = 25ml M1 2.0

Procedures:1.Fill the 500ml volumetric flask with about 20ml of distilled water.2.Pipette 25ml of hydrochloric acid into the volumetric flask.3.By using the wash bottle, fill the volumetric flask with distilled water until the liquid meniscus is even with the graduated mark.4.Cocked and shake the volumetric flask.

Making Standard Solutions by WeighingBasic of making solutions:GCSE Chemistry CD- solutions / curriculum focus / elements, compound, mixtures

Making solutions by weighing: GCSE Chemistry CD- Investigating concentrations / experiment

Activity:

Preparing 100 cm3 of 2.0 M standard sodium hydroxide solution.

Procedures:1.8.0 g of solid sodium hydroxide is weighed.Transferred 8.0g of sodium hydroxide into a beaker containing about 25.0 cm3 of distilled water. The mixture is stirred well to dissolve the solid.3.The solution from the beaker is then carefully poured into a 100 cm3 volumetric flask through a filter funnel.4.Fill the volumetric flask with distilled water until the liquid meniscus is even with the graduated mark.5.Cocked and shake the volumetric flask.