Quantitative Chemistry

Question 1

How to calculate atom economy

Answer 1

(Mr of desired product/ Mr of reactants) x100
Include big numbers for Mr!

Question 2

What is atom economy

Answer 2

Measure of how many atoms in the reactants end up in the useful (desired) product

Question 3

Moles x what = volume (dm cubed)

Answer 3

24

Question 4

How to calculate percentage yield

Answer 4

(Actual yield/ theoretical yield) x100

Measured in grams/ moles

Question 5

What 2 things can the yield of a product be measured in

Answer 5

Grams/ moles

Question 6

What is meant by theoretical yield

Answer 6

The mass of product you expect to be produced

Question 7

What is percentage yield

Answer 7

The actual yield (mass of product) you get in a reaction as a percentage of the theoretical yield (mass of product you expect to be produced)

Question 8

Mr vs Ar

Answer 8

Ar= relative atomic mass (mass number)
Mr = relative formula mass (sum of all relative atomic masses for each atom in the formula)(doesn’t include big numbers as this shows the ratio)

Question 9

Equation linking moles, concentration and volume

Answer 9

Moles= concentration x volume
= (mol/ dm cubed) (dm cubed)

Question 10

Equation linking mass, mr and moles

Answer 10

Mass/ mr = moles

Question 11

At any given temperature and pressure one mole of gas occupies a volume of…

Answer 11

24 dm cubed

Question 12

What is significant about 24 dm cubed

Answer 12

At any given pressure and temperature one mole of gas occupies this volume

Question 13

What is meant by ‘known’ and ‘unknown’ in titration

Answer 13

Both in terms of concentration
Known= known concentration but unknown volume
Unknown= fixed volume but unknown concentration

Doesn’t matter which way round the acid/ alkali is but normally you’re trying to find concentration of acid

Question 14

2 indicators for titration

Answer 14

Methyl orange
Phenolphthalein

Question 15

True or false, you have to do a calculation after carrying out the the titration to find the unknown concentration

Answer 15

True
(Titration tells you the volume of the known concentration but you then need to use this information to do the calculation)

Question 16

End point in titration meaning

Answer 16

When the indicator changes colour
(Neutralisation occurs)

Question 17

Concordant results meaning

Answer 17

3 results within 0.1 cm cubed of each other
(Measured volumes of known from burette)

Question 18

True or false, you must mention variables in titration method

Answer 18

False
No need for variables

Question 19

3 reasons why theoretical yield isn’t always obtained

Answer 19

Some product lost when separated from reaction mixture
Reaction may be reversible
Unexpected side reactions between reactants producing different products