The Mole

Question 1

What is a mole?

Answer 1

A mole of a substance is the amount that contains 6.02x10²³ units, i.e. the same number of units as the number of carbon atoms in 12g of carbon-12.

Question 2

What is Avogadro’s constant?

Answer 2

6.02 x 10²³

This is the number of units (atoms/molecules) in one mole of a substance.

Question 3

• RAM - ?
• RMM - ?
• RFM - ?

Answer 3

• RAM - relative atomic mass (also known as A_r)
  
  • the average mass of the atoms of an element, relative to the mass of an atom of carbon-12
• RMM - relative molecular mass (also known as M_r)
  
  • the mass of a molecule, found by adding the A_rs of the atoms in it
• RFM - relative formula mass (also known as M_r)
  
  • the mass of one formula unit of an ionic compound, found by adding the A_rs of the atoms in the formula

Question 4

What volume does one mole of any gas occupy at r.t.p. (room temperature and pressure)?

Answer 4

24dm³

24 000 cm³

24 litres

Question 5

What equation relates moles, concentration and volume?

Answer 5

amount of solute (mol) = conc. (mol/dm³) x vol. (dm³)

Question 6

What is the empirical formula of a compound?

Answer 6

The formula showing the simplest ratio in which atoms combine, found by experiment.

Question 7

What is % yield and how is it calculated?

Answer 7

Yield is the amount of product you obtain from a reaction.

%yield = actual mass obatined/calculated mass x 100%

Question 8

What is % purity and how is it calculated?

Answer 8

% purity is the percentage of pure product within an impure substance.

% purity of a product = (mass of pure product)/(mass of impure product obtained) x 100%