Chemistry help

Hydrated aluminium sulphate, Al2(SO4)3 . xH2O is used in water treatment.
A student attempts to prepare hydrated aluminium sulphate by the following method.
The student heats dilute sulphuric acid with an excess of solid aluminium oxide.
The student filters off the excess aluminium oxide to obtain a colourless solution of Al2(SO4)3.

State the formulae of the two main ions present in the solution of Al2(SO4)3. [2]

You need two Al for every 3 SO4 to get a charge of 0 overall. So you can switch over those numbers to find the charges. (SO4)2- and Al3+

What does xH2O represent in the formula Al2(SO4)3 . xH2O? [1]

The number of waters of crystallisation for every mole of Al2(SO4)3

Write an equation for the reaction of solid aluminium oxide, Al2O3 with sulphuric acid to form aluminium sulphate and water. Include state symbols. [2]

Balancing equations, when you've already got the reactants and products. Al2O3(s)+3H2SO4(aq)->Al2(SO4)3(aq)+3H2O(l)

The student heats 12.606g of Al2(SO4)3 . xH2O crystals to constant mass.
The anhydrous aluminium sulphate formed has a mass of 6.846g. Use the students results to calculate the value of x.
The molar mass of Al2(SO4)3 = 342.3 gmol-1
[3]
Mass of water lost = 12.606g-6.846g
Moles of water lost = mass of water lost/molar mass of water
Moles of Al2(SO4)3 = 6.846g/ molar mass of Al2(SO4)3
Find the ratio between the number of moles of Al2(SO4)3 to the number of moles of H2O by dividing n: H2O by n:Al2(SO4)3.

Answers and explanations in bold.