GCSE chemistry (C3) homework help- energy change :)

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VioletPhillippo
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#1
Report Thread starter 7 years ago
#1
Hiya,
I'm really struggling with these hwk questions about calaculating energy change as my teacher hasn't explained it very well. Just wondering if anyone can help to explain this or point me in the right direction (as to a method) as I'm not sure where to start. Thanks

1. 100cm^3 HCl containing 0.10mol of HCL was added to 100cm^3 of sodium hydroxide solution containing 0.10mol of NaOH. The temperature of the sodium increased by 7 degrees. Calculate the energy change.

2. 0.10mol of zinc was added to 100cm^3 of copper sulphate solution. The temperature increased by 18 degrees, calculate the energy change.

3. Calculate the energy change for the reaction H(little 2) + F(little 2) ~ 2HF using the given bond energies.

4. " " " " " for the reaction CH(little 2) = CH(little 2) + 3O(little 2) ~ 2CO(little 2) + 2H(little 2)0 using the given bond energies.
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charco
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#2
Report 7 years ago
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(Original post by VioletPhillippo)
Hiya,
I'm really struggling with these hwk questions about calaculating energy change as my teacher hasn't explained it very well. Just wondering if anyone can help to explain this or point me in the right direction (as to a method) as I'm not sure where to start. Thanks

1. 100cm^3 HCl containing 0.10mol of HCL was added to 100cm^3 of sodium hydroxide solution containing 0.10mol of NaOH. The temperature of the sodium increased by 7 degrees. Calculate the energy change.

2. 0.10mol of zinc was added to 100cm^3 of copper sulphate solution. The temperature increased by 18 degrees, calculate the energy change.

3. Calculate the energy change for the reaction H(little 2) + F(little 2) ~ 2HF using the given bond energies.

4. " " " " " for the reaction CH(little 2) = CH(little 2) + 3O(little 2) ~ 2CO(little 2) + 2H(little 2)0 using the given bond energies.
Experimental energy changes are calculated using the formula E=mcΔT

where m is the mass of the solution being heated up and c is 4.2 (the specific heat capacity of water)

One assumption that is always made is that aqueous solutions have the same specific heat capacity as water (4.18kJ kg-1 K-1)

and FYI the way to get a subscript is to surround the item to be subscripted by the [ sub] and [ /sub] tags (without spaces)
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bellabella136
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#3
Ok sooooo...

As mentioned above c=4.2
ΔT is temp change which for 1. is 7
and m= mass of water which for 1. is 100

4.2 x 100 x 7

apply equation to second question too
For bond energies use stoichiometry ratios from given energies (oh **** ur gcse lol). Ok so use the big numbers behind the chemicals to multiply the given bond energies. Don't worry its not too difficult but im awful at explaining things
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VioletPhillippo
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#4
Report Thread starter 7 years ago
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(Original post by bellabella136)
Ok sooooo...

As mentioned above c=4.2
ΔT is temp change which for 1. is 7
and m= mass of water which for 1. is 100

4.2 x 100 x 7

apply equation to second question too
For bond energies use stoichiometry ratios from given energies (oh **** ur gcse lol). Ok so use the big numbers behind the chemicals to multiply the given bond energies. Don't worry its not too difficult but im awful at explaining things
Thanks so much for your help, I think I understand how to work it out using bond energies now. Is there a good method for working out no. 1 and 2? Thanks
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bellabella136
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#5
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Just apply the equation I don't really know any other methods
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