L4 Chemical equations & Moles

Question 1

What is a mole?

Answer 1

= a specific no. of atoms/molecules that makes up a SI unit

= Avogadro’s no.

Question 2

What is Avogadro’s constant?

Answer 2

= 6.02 x 10^23

= the no. of atoms in 12g of C-12

Question 3

What is molar mass (Mr)?

Answer 3

= the mass of one mole of a substance - measured in g/mol

Mr = mass/no. of mol

Question 4

What is molar volume (V)?

Answer 4

= 1 mole of any gas occupies the same volume at standard temperature (273k) and pressure (100kPa)
= 22.4 L

Question 5

What is molarity?

Answer 5

= solution concentration expressed as moles of solute dissolved in one litre of solution - measured in mol/L

Molarity = no. of moles/volume (L)

Question 6

Concentrations of solution equation?

Answer 6

C1 x V1 = C2 X V2

V2 = V1 + the volume added

Question 7

What is the percentage yield equation?

- why is it never 100%?

Answer 7

Percentage yield = (actual yield/theoretical yield) x 100
Never 100% because:
- errors in experimental technique
- side reactions leading to byproducts 
- the reaction reversing 
- product lost during purification