8D 1. Making Standard Solutions (p. 218)

Question 1

What is a standard solution?

Answer 1

It is a solution whose concentration is accurately known

Question 2

What should primary standards be? Give at least 3 out of 6 answers

Answer 2

• they should be solids with high molar masses
• they should be available in a high degree of purity
• they should be chemically stable (neither decompose,nor react with substances in the air)
• they should not absorb water from the atmosphere
• they should be soluble in water
• they should react rapidly and completelywith the other substances when used in titrations

Question 3

Give me examples of substances oftenused in titrations but which are not suitable as primary standards?

Answer 3

• Hydrochloric acid (it is not a solid)

- Sodium hydroxide (it absorbs water vapour and reacts with carbon dioxide from the atmosphere)

Question 4

What is the formula of sulfamic acid?

Answer 4

NH(2) SO(3) H

Question 5

What is the molar mass of sulfamic acid?

Answer 5

97,1 g mol (-1)

Question 6

Can sulfamic acid be used as a primary standard?

Answer 6

Yes (it is readily available for use in acid-base titrations)

Question 7

What is a method used to obtain an accurately known value for the concentration of a solution?

Answer 7

Weighing by difference

Question 8

What is a typical value for the approximate concentration of a solution to be made?

Answer 8

0,1 mol dm(-3)

Question 9

What is a typical value for the approximate volume of a solution to be made?

Answer 9

250 cm(3)