1.2 Amount of Substance Definitions

Question 1

Define Atom economy (and equation)

Answer 1

The measure of the amount of starting material that end up as useful products.

Percentage atom economy = (Molecular mass of desired product/ sum of molecular masses of all reactants) x 100

Question 2

Define Avogadro’s constant

Answer 2

The number of atoms, molecules or ions in one mole of a given substance

Question 3

Define Concentration (and units)

Answer 3

The amount of substance per unit volume. Units given in g/dm^3 or mol/dm^3

Question 4

Define Empirical formula

Answer 4

The smallest whole number ration of atoms of each element in a compound

Question 5

Define Limiting reactant

Answer 5

The reactant that is completely used up since it limits the amount of products formed

Question 6

Define Mole

Answer 6

The mass of a substance containing the same number of units as there are atoms in exactly 12g of carbon-12

Question 7

Define Molecular formula

Answer 7

The actual ration of atoms of each element present in a compound

Question 8

Define Percentage by mass (and equation)

Answer 8

A value representing the concentration of an element in a compound or a component in a mixture

Percentage by mass = (Mass of desired component/ Total mass of mixture) x 100

Question 9

Define Percentage yield (and equation)

Answer 9

The percentage ratio of the actual yield of product from a reaction compared to the theoretical yield

Percentage yield = (Actual yield/Theoretical yield) x 100

Question 10

Define Relative atomic mass

Answer 10

The average mass of an atom of an element compared to 1/12th the mass of an atom of carbon-12

Question 11

Define Relative molecular mass

Answer 11

The average mass of one molecule of an element or compound compared to 1/12th the mass of an atom of carbon-12