Quantitive Chemistry

Question 1

How do you work out the relative formula mass

Answer 1

You times each elements relative atomic mass by the amount of it in the formula then add all of the parts together

Question 2

Percentage mass of an element in a compound =

Answer 2

Ram x no atoms of that element/ x100

Rfm of the whole compound

Question 3

How do you work out the empirical formula

Answer 3

List all of the elements 
Write underneath their masses 
Divide each mass by its ram 
Multiply by ten 
Divide them both by the highest number to get the ratio

Question 4

How do you work out the theoretic yield

Answer 4

Work out the rfm 
Write out the mass you have 
Then 1g
Then the mass you want 
Divide both sides by the mass you have 
Then times by the mass you want to give the theoretical mass of what you should get

Question 5

Percentage yield

Answer 5

Actual yield / X100

Theoretical yield

Question 6

Why is the percentage yield never 100%

Answer 6

Incomplete reactions
Practical loss during preparation (100% of a substance can never be passed between containers)
Unwanted reactions this can be caused by impurities and change in reaction conditions

Question 7

What do scientists want from a reaction

Answer 7

High percentage yield
All products to be useful
Products to be made quickly and safely