3.1.2 Amount of Substance Knowledge

Question 1

define Avogadro’s Constant

Answer 1

number of atoms in 12g of 12C

Question 2

how do you calculate the number of particles?

Answer 2

Number of Particles = Moles x Avogadro’s Constant

Question 3

how do you calculate relative atomic mass?

Answer 3

average mass of one atom of element / 1/12th the mass of a C12 atom

Question 4

how do you calculate relative formula mass?

Answer 4

average mass of one molecule / 1/12th the mass of a C12 atom

Question 5

what is the difference between relative formula and relative molecular mass?

Answer 5

Relative formula mass is used for ionic compounds because, strictly speaking, they don’t exist as simple molecules. Relative molecular mass and relative formula mass can both be calculated and used in the same way.

Question 6

how do you calculate the number of moles?

Answer 6

moles (mol) = mass (g) / molar mass (g/mol)