This discussion is now closed.

Check out other Related discussions

- Chemistry
- Chemistry a level
- Mole Calculations.
- chemistry question help
- MCQ from OCR A-level chemistry
- chem a level question
- Chemistry equation question
- chemistry
- Is finding the moles enough to decide?
- calculating the mass
- Chemistry question
- chem help
- Aspirin
- Don't understand this calorimetry question in regards to the mols
- chemistry help
- Chemistry redox titration question
- hard titration alevel chem Q!
- C3.1.6 Moles, need help!
- %purity
- help with workings pls

I really hope this isn't a hopelessly easy question and I'm just stupid. I just can't see how to go forward.

"4.92g of hydrated magnesium sulphate crystals (MgSO4.nH2O) gave 2.40g of anhydrous magnesium sulphate on heating to constant mass. Work out the formula mass of the hydrated magnesium sulphate and so the value of n.

MgSO4.nH2O ----> MgSO4 + nH2O"

Thanks!

"4.92g of hydrated magnesium sulphate crystals (MgSO4.nH2O) gave 2.40g of anhydrous magnesium sulphate on heating to constant mass. Work out the formula mass of the hydrated magnesium sulphate and so the value of n.

MgSO4.nH2O ----> MgSO4 + nH2O"

Thanks!

Remember no mass can be lost or gained throughout the reaction. With this in mind we can find out the mass of the water on the right side of the equation:

4.92 - 2.40 = 2.52.

The molar mass of water (H2O) is 18 (1+1+16) so to find the number of moles of it you do the molar mass divided by the actual mass:

18.00 / 2.52 = 7.14

The value will never be perfect because of experimental error, so round it to 7. So there are 7 moles of water on the right side of the equation, so n = 7.

Hope that helps

4.92 - 2.40 = 2.52.

The molar mass of water (H2O) is 18 (1+1+16) so to find the number of moles of it you do the molar mass divided by the actual mass:

18.00 / 2.52 = 7.14

The value will never be perfect because of experimental error, so round it to 7. So there are 7 moles of water on the right side of the equation, so n = 7.

Hope that helps

Tomsey mass/Mr= moles

Coincidentally, from my quick calculation, your answer is correct!

OP, work out the moles of water then the moles of magnesium sulphate. Then work out howmany waters to 1 mole of MgSO4, and this is n.

eg if you get 0.25 moles MgSO4 and 0.5 water, this works out 1:2. Methodically, divide by the smaller number to work out the ratio as you often get long numbers.

Coincidentally, from my quick calculation, your answer is correct!

OP, work out the moles of water then the moles of magnesium sulphate. Then work out howmany waters to 1 mole of MgSO4, and this is n.

eg if you get 0.25 moles MgSO4 and 0.5 water, this works out 1:2. Methodically, divide by the smaller number to work out the ratio as you often get long numbers.

Original post by squishedbanana

Original post by silent ninja

Tomsey mass/Mr= moles

Coincidentally, from my quick calculation, your answer is correct!

OP, work out the moles of water then the moles of magnesium sulphate. Then work out howmany waters to 1 mole of MgSO4, and this is n.

eg if you get 0.25 moles MgSO4 and 0.5 water, this works out 1:2. Methodically, divide by the sma number to work out the ratio as you often get numbers.

Coincidentally, from my quick calculation, your answer is correct!

OP, work out the moles of water then the moles of magnesium sulphate. Then work out howmany waters to 1 mole of MgSO4, and this is n.

eg if you get 0.25 moles MgSO4 and 0.5 water, this works out 1:2. Methodically, divide by the sma number to work out the ratio as you often get numbers.

Original post by tomsey11

Remember no mass can be lost or gained throughout the reaction. With this in mind we can find out the mass of the water on the right side of the equation:

4.92 - 2.40 = 2.52.

The molar mass of water (H2O) is 18 (1+1+16) so to find the number of moles of it you do the molar mass divided by the actual mass:

18.00 / 2.52 = 7.14

The value will never be perfect because of experimental error, so round it to 7. So there are 7 moles of water on the right side of the equation, so n = 7.

Hope that helps

4.92 - 2.40 = 2.52.

The molar mass of water (H2O) is 18 (1+1+16) so to find the number of moles of it you do the molar mass divided by the actual mass:

18.00 / 2.52 = 7.14

The value will never be perfect because of experimental error, so round it to 7. So there are 7 moles of water on the right side of the equation, so n = 7.

Hope that helps

Thanks I had a similar question and you really helped

- Chemistry
- Chemistry a level
- Mole Calculations.
- chemistry question help
- MCQ from OCR A-level chemistry
- chem a level question
- Chemistry equation question
- chemistry
- Is finding the moles enough to decide?
- calculating the mass
- Chemistry question
- chem help
- Aspirin
- Don't understand this calorimetry question in regards to the mols
- chemistry help
- Chemistry redox titration question
- hard titration alevel chem Q!
- C3.1.6 Moles, need help!
- %purity
- help with workings pls

Latest

Trending