5.32 - Making standard solutions

Question 1

What is a standard solution?

Answer 1

A solution of which the concentration is accurately known

Question 2

What are primary standards?

Answer 2

Substances used to make a standard solution by weighing

Question 3

What is the method for making a standard solution of sulfamic acid?

Answer 3

• Add 2.5g to a weighing boat
• Add the acid to a beaker, and add 100cm3 of deionised water
• Stir until the sulfamic acid has fully dissolved
• Transfer this, including the washings, into a volumetric flask, and fill it up to the mark with more deionised water
• Invert the bottle several times to make the solution uniformed

Question 4

If there is 2.5g of sulfamic acid dissolved in 250cm3 of deionised water, what is the concentration of the solution?

Answer 4

Mr of Na2SO3H = 97.1

Moles of Na2SO3H = 2.5g/97.1 = 0.0257 moles

Concentration = 0.0257/(250/1000) = 1.03mol dm-3