Finding sulfate ion concentration when mixing Na2SO4 and Al2(SO4)3 solutions

[geffman1]

Homework Statement

hey i really can't do this question, can anyone help. A mixture was made from solutions of sodium sulfate and aluminium sulfate.
311 mL of 0.500 M Na2SO4 solution and 190 mL of 0.300 M Al2(SO4)3 solution were mixed together. Calculate the concentration of SO42- ions in the final solution?


anyhelp would be appreciated. thanks

The Attempt at a Solution

 

[symbolipoint]

How many moles of Na₂SO₄ ? How many moles of SO₄ does each mole of the salt have?

How many moles of Al₂(SO₄)₃ ? How many moles of Sulfate does each mole of this salt have?

 

[geffman1]

moles of Naso4=0.1555
moles of Al(So4)3=0.057

How do i work out the number of moles of So4 ions?

 

[Borek]

Al₂(SO₄)₃ - how many Al³⁺ per molecule? How many SO₄^2- per molecule?

Al₂(SO₄)₃ - how many moles Al³⁺ per mole of salt?

 

[geffman1]

2 Al /molecule 3 SO4molecule.
im not sure if this is right--mole of al=26.98/(26.98x2)+(3x32.02)+(12x16)=0.0788mol?

 

[Borek]

No, no need for molar masses.

Mole is just an ovegrown dozen.

If there is one exhaust in car, how many exhausts in dozen cars?

If there is one exhaust in car, how many exhausts in mole of cars?