Amount of substance

Question 1

Define relative atomic mass (Ar)

Answer 1

The mean mass of an atom of an element relative to 1/12th of the mean mass of an atom of carbon-12

Question 2

Defne relative molecular mass (Mr)

Answer 2

The mean mass of a molecule of a compound relative to 1/12th of the mean mass of an atom of carbon-12

Question 3

How do you find the number of particles present in a sample of substance (with known mass)?

Answer 3

Number of particles = moles x avogadros constant

Question 4

What is the ideal gas equation?

Answer 4

pV=nRT = (mRT/Mr)

p - pascals
V - m3
n - moles
m - grams
T - kelvin
R - 8.31 JK-1mol-1

Question 5

Define empirical formula

Answer 5

simplest whole number ratio of atoms of each element in a compound

Question 6

Define molecular formula

Answer 6

the true number of each atom in the molecule.

Question 7

How can you find the molecular formula using the empirical formula?

Answer 7

Mr of molecule / empirical Mr = multiplier

Question 8

How do you calculate percentage yield?

Answer 8

% yield = (experimental mass / theoretical mass) x100

Question 9

How do you calculate atom economy?

Answer 9

% atom economy = (Mr of desired product / Mr of reactants) x100