3. Solutions, ionisation and non-covalent interactions

Question 1

When is a solution produced?

Answer 1

Produced when a solid, liquid or gas (solute) dissolves in a liquid

Question 2

What does ‘dissolve’ imply about a component?

Answer 2

Component molecules of the solid are separated and the compound is present as single molecules

Question 3

When is a suspension produced?

Answer 3

Molecules of the compound are present as aggregates containing many individual molecules

Question 4

What is concentration? What is the equation for it?

Answer 4

Amount of solute per unit volume of solvent

Concentration= Amount/ Volume

Question 5

What is the unit ppm equivalent to?

Answer 5

ppm= parts per million= g of solute per 10^6 g of solution

Aqueous solutions= mg L^-1

Question 6

Why does amount not equal concentration?

Answer 6

The same amount of solute can be used to make a solution of high concentration (small volume) or solution of low concentration (large volume)

Question 7

What is molarity? What is the equation for it?

What is the unit favoured for it?

Answer 7

Molarity: Based on gram molecular (atomic, ionic) weight of the compound
Defined to contain the same number of molecules (Avogadro’s number)= 1 mole

Molarity (M)= Amount (moles)/ Volume (litres)

Unit: moles dm^-3 but is not used in biological/biochemical literature therefore:

1mM= 10^-3 M therefore 1M= 1000mM 
1μM= 10^-6 M therefore 1M= 1000000μM