calculations ✓

Question 1

what does the symbol (s) mean ?

Answer 1

solid

Question 2

what does the symbol (l) mean ?

Answer 2

liquid

Question 3

what does the symbol (g) mean ?

Answer 3

gas

Question 4

what does the symbol aq) mean ?

Answer 4

aqueous (dissolved in water)

Question 5

how do you find the Ar of an element ?

Answer 5

the bigger number

Question 6

how do you find the Mr of a compound ?

Answer 6

add the elements Ar’s together

Question 7

what is the calculation when finding moles when using mass ?

Answer 7

moles = mass ÷ Ar or Mr

Question 8

what is the calculation to find the percentage yield ?

Answer 8

(actual yield ÷ theoretical yield) X 100

Question 9

what is the difference between the empirical and molecular formulae ?

Answer 9

empirical = simplest ration 
molecular = actual chemical formula

Question 10

what is the rearranged calculation so you can find the Mr ?

Answer 10

Mr = mass ÷ moles

Question 11

what is the rearranged calculation so you can find the mass ?

Answer 11

mass = Mr x moles

Question 12

what is an experiment to determine the formula of metal oxide by combustion, magnesium oxide ?

Answer 12

• get a crucible and heat it until its red hot to make sure its clean
• leave the crucible to cool then weigh it with its lid
• add some magnesium ribbon (weight of magnesium is the weight now minus the weight before)
• heat the crucible containing the magnesium and put lid on but leave small gap for oxygen to enter
• heat units magnesium ribbon has gone white
• allow to cool and reweigh
• mass of magnesium oxide (the reading atm minus the initial reading of the mass of crucible and lid)