AMOUNT OF SUBSTANCE

Question 1

How many atoms of carbon-12 are found in 1 mole of carbon-12?

Answer 1

6.02 x 10^23

Question 2

What are the units of molar mass?

Answer 2

g mol-1

Question 3

How do you find the number of moles of a subance?

Answer 3

mass / molar mass

n = m/ M

Question 4

How do you find the molar mass of an element?

Answer 4

It is the relative atomic mass in g

i.e one mole of C = 12.0g
one mole of H = 1.0g

Question 5

What is meant by the empirical formula?

Answer 5

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

Question 6

How to find Mr of a substance (Relative molecular mass)

Answer 6

Add the atomic masses of the elements making up the molecule

Question 7

Name 2 simple molecules

Answer 7

Water

Carbon dioxide

Question 8

What happens when you heat blue crystals of hydrated Copper ll Sulfate?

Answer 8

The bonds holding the water within the crystal are broken
The water is driven off
Leaving behind white anhydrous copper ll sulfate

Question 9

How can we be sure that all water has been removed from a substance?

Answer 9

Heat the substance up repeatedly until the mass of the residue no longer changes

Question 10

Why might the water of crystallisation be inaccurate?

Answer 10

Not all the water has been lost from the crystal.
If the hydrated and anhydrous forms are similar colours, it isn’t easy to tell when all the water has been removed.

They assume that there is no further decomposition
Many salts decompose further when heated
This is difficult to judge is there is no colour change

Question 11

How many ml in 1 cubic centimetre?

Answer 11

1cm^3 = 1ml

Question 12

1 dm^3 and 1 litre is the same as how many ml?

Answer 12

1 dm^3 = 1000 cm^3 = 1000 ml = 1 litre

Question 13

What is concentration measured in?

Answer 13

Moldm^-3

Question 14

What is meant by concentration?

Answer 14

The concentration of a solution is he amount of solute, in moles, dissolved in each 1dm^3 (1000 c^3) of solution.

aka. A 1 moldm^-3 solution contains 1 mole of solute dissolved in 1dm^3 of solution

Question 15

What is volume measured in?

Answer 15

dm^3

Question 16

What is the equation linking n, V and c?

Answer 16

n = c x v

if the question is given in cm^3 and requires answer to be in dm^3:

n = c x (V in cm^3 / 1000)

Question 17

What is a standard solution?

Answer 17

A standard solution is a solution of known concentration.

Question 18

What are the conditions at RTP?

Answer 18

Temp = 20 degrees
Pressure = 1 atm
Molar gas volume = 24.0 dm^3 mol^-1

Question 19

What is the ideal gas equation?

Answer 19

pV = nRT

p = pressure
V = volume
n = moles
R = idealgas constant = 8.31 J mol-1 k-1
T = Temp

Question 20

How to convert degrees into Kelvin

Answer 20

+273

Question 21

How do you change from cm^3 to m^3?

Answer 21

x 10^-6

Question 22

How do you change from dm^3 to m^3?

Answer 22

x 10^-3

Question 23

How do you change from kPa to Pa?

Answer 23

x 10^3

Question 24

What are the correct units for any quantities when using the ideal gas equation?

Answer 24

Pa
K
m^3

Question 25

What is meant by the theoretical yield?

Answer 25

The maximum possible amount of product

Question 26

Why is it hard to form the maximum possible amount of product?

Answer 26

The reaction may not have gone to completion

Other reactions may have taken place alongside the main reaction

Purification of the product may result in loss of some product

Question 27

What is the equation for percentage yield?

Answer 27

% yield = Actual yield / Theoretical yield x100

Question 28

How do you work out which reactant is in excess?

Answer 28

Work out the amount in moles of each reactant
The larger the number of moles, the faster it will be used up
So the limiting reagent will be the reactant that is used up.

Question 29

What is meant by atom economy?

Answer 29

The amount of reactant turning into the desired product

Question 30

What does having a high atom economy mean?

Answer 30

1. the reaction produces a large proportion of desired products and few unwanted waste products
2. They are important for sustainability as they make the best use of natural resources