Question

A 450 g sample of Al₂(SO₃)₃ is reacted with 410 g of Ca(OH)₂. Equation: Al₂(SO₃)₃(aq) + 3Ca(OH)₂ (aq) → 2Al(OH)₃(s) + 3CaSO₃(s).

How many grams of CaSO₃ will be produced?

Answer 1

So firstly, to do this you will need to work out the moles of either Al2(SO3)3 or Ca(OH)2 (it doesn't matter which one as they will both have the same no. of moles in the end).

Lets use Ca(OH)2. So, firstly we would have to work out the moles of this substance, so we can use the moles of that substance to find the grams of another in the same equation (its easy to use the moles to find the amount in grams of something else).

So, to work out the moles you will need to do this: moles = mass/molar mass
(You can work out the molar mass of Ca(OH)2 by adding the elements atomic mass number on the periodic table together, e.g. 1 Calcium (40.1)+ 2 Oxygen's (16+16) + 2 Hydrogen's (1+1) and mass will be 410g given in the question)

Once you have the moles, that will be the moles of CaSO3, as they both have a '3' in front of their compounds. This means there are THREE lots of those compounds. Moles cannot be added of created, so one moles of something will create one moles of another (if you worked out the moles of Al2(SO3)3 then you would have to times the amount of moles by 3, because there is no number in front Al2(SO3)3 meaning there is ONE lot of those, and there are THREE lots of CaSO3).

So the moles of Ca(OH)2 will be the same amount of moles for CaSO3.

Now you have the amount in moles of CaSO3, you can convert moles into amount in grams. To do this you will have to use this equation: mass = moles x molar mass (of CaSO3).

Once you have done this, you should end up with your answer in grams!
Good luck :)