# Chemistry A level- question

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Thread starter 1 month ago
#1
17.1 g of aluminium sulfate, Al2 (SO4) 3, was dissolved in water.

Calculate the number of sulfate ions, SO42–, present in the solution formed. [Assume the molar mass of Al2 (SO4) 3 is 342 g mol–1 and the Avogadro Constant is 6 × 1023 mol–1.]

A 3 × 1021
B 1 × 1022
C 3 × 1022
D 9 × 1022

How do I solve this?
0
1 month ago
#2
How many moles of sulfate ions are in one mole of aluminium sulfate?
1
1 month ago
#3
(Original post by _gxg)
17.1 g of aluminium sulfate, Al2 (SO4) 3, was dissolved in water.

Calculate the number of sulfate ions, SO42–, present in the solution formed. [Assume the molar mass of Al2 (SO4) 3 is 342 g mol–1 and the Avogadro Constant is 6 × 1023 mol–1.]

A 3 × 1021
B 1 × 1022
C 3 × 1022
D 9 × 1022

How do I solve this?
Calculate the number of moles of Al2(SO4)3
Moles = mass/molar mass
This will tell you how much of Al2(SO4)3 there is, however, the question is asking for (SO4)2-...
So for every Al2(SO4)3, there's 3 (SO4)2-, so you are effectively multiplying the moles of Al2(SO4)3 by 3 to get the moles of (SO4)2-
From there, apply Avogadro's constant to get your final answer.
1
1 month ago
#4
(Original post by _gxg)
17.1 g of aluminium sulfate, Al2 (SO4) 3, was dissolved in water.

Calculate the number of sulfate ions, SO42–, present in the solution formed. [Assume the molar mass of Al2 (SO4) 3 is 342 g mol–1 and the Avogadro Constant is 6 × 1023 mol–1.]

A 3 × 1021
B 1 × 1022
C 3 × 1022
D 9 × 1022

How do I solve this?
I want to do a level chem this seems so tricky what the f
0
1 month ago
#5
(Original post by goneclear)
I want to do a level chem this seems so tricky what the f
Nah, this is pretty straight forward. How things look when you're unfamiliar with them can put you off, but honestly it always looks worse than it is.
1
1 month ago
#6
(Original post by EierVonSatan)
How many moles of sulfate ions are in one mole of aluminium sulfate?
hmm i didnt think of this
0
1 month ago
#7
(Original post by goneclear)
I want to do a level chem this seems so tricky what the f
Just slightly advanced from GCSE mole calculations, but don't be thrown off by how a question looks - if you are passionate and willing to do a subject then it will be fine.
0
1 month ago
#8
(Original post by EierVonSatan)
Nah, this is pretty straight forward. How things look when you're unfamiliar with them can put you off, but honestly it always looks worse than it is.
I agree. I think the lack of superscripts/subscripts in the OP also makes it harder to comprehend.
2
Thread starter 1 month ago
#9
(Original post by Fruit09)
Calculate the number of moles of Al2(SO4)3
Moles = mass/molar mass
This will tell you how much of Al2(SO4)3 there is, however, the question is asking for (SO4)2-...
So for every Al2(SO4)3, there's 3 (SO4)2-, so you are effectively multiplying the moles of Al2(SO4)3 by 3 to get the moles of (SO4)2-
From there, apply Avogadro's constant to get your final answer.
thank you so much!
0
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