Moles II - Molecular and Empirical Formulae and Hydrated Salts

Question 1

empirical formula

Answer 1

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

Question 2

molecular fomula

Answer 2

the number and type of atoms of each element in a molecule

Question 3

3 steps for finding empirical formula

Answer 3

1. find moles
2. divide by smallest to get ratio
3. write as smallest whole number ratio

Question 4

formula for % mass

Answer 4

mass of element in compound/total mass of compound x 100

Question 5

water of crystallisation

Answer 5

water molecules locked aaround ions in an ionic compund crystallised from a solution

Question 6

hydrated salt

Answer 6

a salt containing water of crystallisation

Question 7

anhydrous salt

Answer 7

a salt containing no water of crystallisation after water is driven off as steam when heated

Question 8

6 steps of finding the formula of a hydrated salt (ratio)

Answer 8

1. mass of water lost
2. mles of water lost
3. mass of anhydrous salt
4. moles of anhydrous salt
5. divide moles of water by moles of salt
6. write out formula

Question 9

what is the effect of calculated number of H2O (x) if not all water lost?

Answer 9

x gets smaller

Question 10

what is the effect of calculated number of H2O (x) if thermal decomposition occurs

Answer 10

x gets bigger