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# Chem question , Magnesium sulfate watch

1. hey all i need help with a chem question , so we did an experiment about water crystallization in magnesium sulfate . By heating it up: here are the results :

.mass of crucible : 5.41(grams)
.mass of crucible+Mgso4.xH20 :9.61(grams)
.mass after 1st heating : 7.60(grams)
.Mass after 2nd heating: 7.51(grams)
.Mass of crucible+MgSO4: 7.51(grams)
.Mass of MgSO4.xH20 : 4.20 (grams)

.Mass of MgSO4 : unknown
.Mass of H20 : unknown

how do i calculate the mass for magnesium and water , any help appreciated (and more information)
2. anyone?
3. Take the mass of the crucible away from the mass of mgso4 and the crucible. You should be able to do the rest from there.
4. (Original post by VictiniCup)
Take the mass of the crucible away from the mass of mgso4 and the crucible. You should be able to do the rest from there.
thats how i found the mass of MgSO4.xH20 , is it the same ?
5. (Original post by VictiniCup)
Take the mass of the crucible away from the mass of mgso4 and the crucible. You should be able to do the rest from there.
??
6. anyone else ?
7. plz someone help
8. Find the RMM of MgSO4 and H2O.

Find how many moles of sulphate and water there is.

Find the molar ratio of magnesium sulphate to water.

The answer id non integer because MgSO4 can have different numbers of water ligands.
9. (Original post by Maker)
Find the RMM of MgSO4 and H2O.

Find how many moles of sulphate and water there is.

Find the molar ratio of magnesium sulphate to water.

The answer id non integer because MgSO4 can have different numbers of water ligands.
how can i calculate moles if i dont have mass ?
how can i calculate moles if i dont have mass ?
The mass of MgSO4 is the mass of the residue after the second heating
11. (Original post by Maker)
Use the emperical formula.
what do i divide the rmm by though
12. (Original post by Maker)
The mass of MgSO4 is the mass of the residue after the second heating
oh ok , but how is the mass of MgSO4 alone is bigger than the mass of MgSO4.xH2O
oh ok , but how is the mass of MgSO4 alone is bigger than the mass of MgSO4.xH2O
14. (Original post by Maker)
isn't the mass 7.51 cause it's the same as 2nd heating
15. (Original post by Maker)
right ?
isn't the mass 7.51 cause it's the same as 2nd heating
You need to subtract the weight of the crucible.
17. (Original post by Maker)
You need to subtract the weight of the crucible.
oh ok , would that mean the mass of water is 0.89 Grams ( mass of Mgso4.xh20 - 3.31 , which is the mass of mgso4)
18. I would do this:
Mass of crucible and MgSO4.H2O = 9.61
Mass of H2O = 9.61- 7.51(Mass of crucible and MgSO4 after 2nd heating) = 2.1
Mass of MgSO4.H2O = 4.2 -2.1 =2.1
so you have 2.1g of H2O and 2.1g of MgSO4

(might be wrong, but that is what I would do)
19. (Original post by ScienceWise2017)
I would do this:
Mass of crucible and MgSO4.H2O = 9.61
Mass of H2O = 9.61- 7.51(Mass of crucible and MgSO4 after 2nd heating) = 2.1
Mass of MgSO4.H2O = 4.2 -2.1 =2.1
so you have 2.1g of H2O and 2.1g of MgSO4

(might be wrong, but that is what I would do)
I did the same, I get the number of water molecules per MgSO4 molecule as 6.6:1 so its probably mixture of hexahydrate and heptahydrate.
20. (Original post by Maker)
I did the same, I get the number of water molecules per MgSO4 molecule as 6.6:1 so its probably mixture of hexahydrate and heptahydrate.
you know what idc anymore i'm just gonna write that down , thanks for the help

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