Amount of substance

Question 1

What is amount of substance?

Answer 1

The name given to counting the number of particles in a substance - the unit is the mole

Question 2

What is the mole?

Answer 2

The unit for amount of substance. The amount of substance that conatins 6.02 x 10^23 particles

Question 3

What is Avogadro’s constant?

Answer 3

The number of particles in 1 mole of carbon-12
Na = 6.02 x 10^23

Question 4

What is molar mass?

Answer 4

The mass per mole of a substance

Question 5

What is the moles and molar mass equation?

Answer 5

n = m/ Mr

n = moles
m = mass g
Mr = molar mass gmol^-1

Question 6

What is molar gas volume?

Answer 6

The volume occupied by one mole of any gas at RTP. It has a value of 24 dm^3

Question 7

What is empirical formula?

Answer 7

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

Question 8

What is molecular formula?

Answer 8

The number and type of atoms of each element in a molecule

Question 9

What is water of crystallisation?

Answer 9

Water molecules that form part of the crystalline structure of a compound

Question 10

What does does anhydrous mean?

Answer 10

A crystalline compound containing no water

Question 11

What does hydrated mean?

Answer 11

A crystalline compound that contains water

Question 12

What is the procedure to find the formula of a hydrated salt?

Answer 12

Question 13

What are the assumptions made when finding the formula of a hydrated salt?

Answer 13

• All of the water has been lost
• No further decomposition occurs

Question 14

What is the molar gas volume?

Answer 14

n = V/ 24

in dm^3 at RTP

Question 15

What is the moles, concentration and volume equation?

Answer 15

n =cv

n = moles mol
c = concentration mol dm^-3
v = volume dm^3

Question 16

What is the ideal gas equation?

Answer 16

pV = nRT

p = pressure Pa
V = volume m^3
n = moles mol
R = ideal gas constant = 8.314
T = temperature K

Question 17

What is stoichiometry?

Answer 17

The ratio of amount of substance of each substance in mol

Question 18

What is theoretical yield?

Answer 18

The maximum possible amount of product

Question 19

What is the equation for percentage yield?

Answer 19

Percentage yield = (actual yield / theoretical yield) x100%

Question 20

Why is theoretical yield difficult to reach?

Answer 20

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

Question 21

What is the limiting reagent?

Answer 21

The reactant that is not in excess - has the most mole in stoichemoetry

Question 22

What is atom economy?

Answer 22

A measure of how well atoms have been utilised

Question 23

What is the equation for atom economy?

Answer 23

Atom economy = (sum of Mr’s of desired products / sum of Mr’s of all products) x 100

Question 24

How do you find a relative molecular mass experimentally using pV = nRT?

Answer 24

Question 25

How can you experimentally identify and unknown metal?

Answer 25

Question 26

The higher the atom economy of a reactant, the _____ sustainable it is

Answer 26

More

Less energy and reactants are required to form more products. Despite this, reactions with a high atom economy may have a poor percentage yield; efficiency is dependant on both of these factors