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# Solubility of Ionic substances

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1. The equation from what I have learnt is:

Delta H solution= Sum of delta H hydration - dHlattice formation

I keep getting these kind of questions wrong

E.g.

http://qualifications.pearson.com/co...e_20140113.pdf

Question 4
2. Do you know how to draw Hess cycles for these types of questions?

(Original post by Dinaa)
The equation from what I have learnt is:

Delta H solution= Sum of delta H hydration - dHlattice formation

I keep getting these kind of questions wrong

E.g.

http://qualifications.pearson.com/co...e_20140113.pdf

Question 4
3. (Original post by Poooky)
Do you know how to draw Hess cycles for these types of questions?
Same as for any other process:

NaCl(s) ----> Na+(aq) + Cl-(aq) ΔHsolution

NaCl(s) ---> Na+(g) + Cl-(g) ----> Na+(aq) + Cl-(aq) (i) ΔHlattice enthalpy --- > (ii) ΔHhydration
4. (Original post by charco)
Same as for any other process:

NaCl(s) ----> Na+(aq) + Cl-(aq) ΔHsolution

NaCl(s) ---> Na+(g) + Cl-(g) ----> Na+(aq) + Cl-(aq) (i) ΔHlattice enthalpy --- > (ii) ΔHhydration
I was trying to get OP to work through it I thought if she could draw it out, she'd be able to see where she went wrong- usually it's either using the wrong signs or forgetting about balancing the equation ie that there are 2 Cl-'s involved in the reaction- hopefully that helps Dinaa
5. (Original post by Poooky)
I was trying to get OP to work through it I thought if she could draw it out, she'd be able to see where she went wrong- usually it's either using the wrong signs or forgetting about balancing the equation ie that there are 2 Cl-'s involved in the reaction- hopefully that helps Dinaa

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