Amount Of Substance

Question 1

Define relative atomic mass

Answer 1

The mean mass of an atom of an element, relative to 1/12th of a carbon 12 atom

Question 2

Define relative molecular mass

Answer 2

The mean mass of a molecule of a compound, relative to 1/2th ofthe mean mass of a carbon 12 atom

Question 3

Define relative formula mass

Answer 3

Relative formula mass is the same as relative molecular mass but just refers to ionic compounds

Question 4

What is avogadro’s constant?

Answer 4

The number of atoms in a mole
6.022x 10^23

Question 5

What are the units for concentration?

Answer 5

Mol dm^-3

Question 6

What are the two equations used to calculate number of moles?

Answer 6

Moles = concentration x volume
Moles = mass / Mr

Question 7

What is the ideal gas equation and state the units for which each compound is measured

Answer 7

Pv=nRT

Pressure measured in Pa
Volume measured in m^3
Moles measured in moles
Gas constant measured in J/K mol
Temperature measured in K

Question 8

Define molecular formula

Answer 8

The true number of each atom in the molecule

Question 9

Define empirical formula

Answer 9

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

Question 10

What is the relationship between empirical and molecular formula?

Answer 10

Empirical is a factor of molecular
When you multiply empirical by the correct multiplier you will get the molecular formulas

Multiplier= molecular mass / empirical mass

Question 11

How do you calculate percentage atom economy?

Answer 11

( Mass of desired products / total reactant mass ) x 100

Question 12

What is the equation for percentage yield?

Answer 12

( Moles of certain product / theoretical maximum ) x100

Question 13

Define uncertainty
How do you calculate uncertainty?

Answer 13

Uncertainty is the range of possible values that the true value of measurement lies within

% uncertainty = ( uncertainty / measurement ) x100

You can decrease uncertainty by measuring in larger volumes and transferring less often… etc

Question 14

State the economic, environmental and ethical advantages for society and industry of producing chemical processes with high atom economy.

Answer 14

Less wastage = less pollutant (environmental)
Greater yield = more profit (economic)
Limited resources so it’s not wasteful (ethical)
Cheaper to make = cheaper to buy ( economic and social)