Amount of Substance

Question 1

What is molecular formula?

Answer 1

Actual number of atoms of each element in a compound

Question 2

What is empirical formula?

Answer 2

simplist ratio of atoms of each element in a compound

Question 3

What is the formula for atom economy

Answer 3

(mr of desired products/ mr of all products ) x 100

Question 4

what is the calculation for NUMBER of moles

Answer 4

number of molecules/ avogadro

Question 5

What is %yield?

Answer 5

Tells us about the practical efficiency of the process

Question 6

What is the formula for % yield?

Answer 6

(actual yield/mass/ theoretical mass) x 100

Question 7

What is the formula for actual yield?

Answer 7

(percentage yield x theoretical yield) / 100

Question 8

What is the equation for %purity?

Answer 8

(actual mass/impure mass) x 100

Question 9

what is the formula for apparatus error?

Answer 9

(margin of error/quantity) x100

Question 10

what is the ideal gas equation?

Answer 10

pv = nRt

Question 11

How do you work out empirical formula

Answer 11

• divide the percentage of the element by its Mr
• Work out the ratio of all elements by dividing by the smallest number
• Ratio should be whole numbers

Question 12

How do you calculate molecular formula

Question 13

how can you calculate the limiting/excess reactant?

Answer 13

• work out the moles of both reactants
• reactant with the smallest value is limiting

Question 14

how do you calculate the average titre

Answer 14

titres (volume) within 0.1 of eachother

subtract them then divide by 2

Question 15

what is a back titration?

Answer 15

A base is treated with an excess of acid on the leftover acid is titrated (vice versa)

You can then work back to find the original base that reacted

Question 16

How can you use the limiting reagent to work out the maximum mass of products that can be made?

Answer 16

• after working out the limiting use the ratio to calculate moles of the product
• use moles to calculate mass