chemical calculations

Question 1

what is relative atomic mass

Answer 1

average mass of an atom relative to 1/12 the mass of a carbon-12 atom

Question 2

what is relative molecular mass

Answer 2

average mass of one molecule of a substance relative to 1/12 the mass of a carbon-12 atom

Question 3

what is relative formula mass

Answer 3

average mass of one unit of a compound relative to 1/12 the mass of a carbon-12 atom

Question 4

percentage mass

Answer 4

formula mass of element / formula mass of compound x 100%

Question 5

number of particles in a mole / avogadro’s constant

Answer 5

6.02 x 10^23

Question 6

calculating moles from mass

Answer 6

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

Question 7

calculating moles using volume (of gases)

Answer 7

moles = volume (dm3) / 24

Question 8

calculating moles using concentration

Answer 8

moles = concentration (mol/dm3) x volume (dm3)

Question 9

calculating percentage yield

Answer 9

actual yield / theoretical yield x 100%
percentage yield is ALWAYS ≤100%

Question 10

calculating percentage purity

Answer 10

mass of pure substance / mass of sample x 100%

Question 11

empirical formula table

Answer 11

mass /g
number of moles /mol
mole ratio
simplest whole number ratio