Chapter 3 Amount of substance

Question 1

What is relative molecular mass?

Answer 1

relative molecular mass compares the mass of a molecule with the mass of an atom of carbon-12

Question 2

What is relative formula mass?

Answer 2

relative formula mass compares the mass of a formula with the mass of an atom of carbon-12

Question 3

What is ‘Amount of substance’

Answer 3

The number of particles in a substance measuring in a unit called mole

Question 4

What is one mole?

Answer 4

The amount of a substance that contains (6.02x10^23) particles

Question 5

What is Avogardro’s constant?

Answer 5

6.02x10^23 –> the number of particles in each mole of carbon-12

Question 6

What is Molar mass?

Answer 6

The mass per mole of a substance and gives a convient way of linking moles with mass for any chemical substance

Question 7

What is the equation for Amount of substance using Molar mass?

Answer 7

Amount of substance = mass / Molar mass

Question 8

What is the molecular formula?

Answer 8

The number of atoms of each element in a molecule

Question 9

What is the empirical formula?

Answer 9

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

Question 10

What is molar gas volume?

Answer 10

The volume per mole of gas molecules at a stated temperature and pressure

Question 11

What are the two assumptions when calculating the formula of a hydrated salt?

Answer 11

Assumption 1 - All of the water has been lost

Assumption 2 - No further decomposition

Question 12

What is water of crystallisation?

Answer 12

The water in a lattice

Question 13

What is the equation for Amount of stubstance using Concentration?

Answer 13

Amount of substance = Concentration X Volume(dm3)

Question 14

What is standard solution?

Answer 14

A solution of known concentration

Question 15

What is molar gas volume?

Answer 15

The volume per mole of gas molecules at a stated temperature and pressure

Question 16

What is the equation for Amount of substance using Molar gas volume?

Answer 16

Amount of substance = Volume / Molar gas volume

Question 17

What is the Ideal gas equation

Answer 17

pV = nRT

Question 18

What does (p) represent in the ideal gas equation?

Answer 18

Pressure measured in Pa

Question 19

What does (V) represent in the ideal gas equation?

Answer 19

Volume measured in m3

Question 20

What does (n) represent in the ideal gas equation?

Answer 20

amount of gas molecules measured in mol

Question 21

What does (R) represent in the ideal gas equation?

Answer 21

Constant of 8.314

Question 22

What does (T) represent in the ideal gas equation?

Answer 22

Temperature measured in K

Question 23

What is theoretical yield?

Answer 23

The maximum possible amount of product

Question 24

What are the 3 main factors affecting theoretical yield?

Answer 24

• The reaction may not have gone to completion
• Other reactions may have taken place alongside the main reaction
• Purification of the product may lresult in loss of some product

Question 25

What is the equation for percentage yield?

Answer 25

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

Question 26

In a reaction, what is a limiting reagent?

Answer 26

The reactant that is not in excess and will be completely used up first and stop the reaction

Question 27

What is atom economy?

Answer 27

A measure of how well atoms have been utilised

Question 28

What is the equation for calcualting atom economy?

Answer 28

Atom economy = (Sum of molar masses of desired products / Sum of molar masses of all products) x 100