Zinc will displace copper from copper (II) sulphate solution according to the following equation:
CuSO_{4}(aq) + Zn(s) > Cu(s) + ZnSO_{4}(aq)
Ifan excess of zinc powder is added to 50 cm^{3} of 1.0moldm^{3} copper(II) sulphate, the temperature increases by 6.3 ^{o}C. Calculate the enthalpy change for the reaction.
Assuming ρ =1.0 gcm^{3} and c = 4.18 Jg^{1}K^{1}
^{someone pls talk me through how to do this}
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thefatone
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 13032016 11:44
Last edited by thefatone; 13032016 at 12:54. 
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 13032016 12:12
I'll bet you've done loads of examples in class. What are you thoughts on how to do it?

thefatone
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 13032016 12:54
(Original post by Pigster)
I'll bet you've done loads of examples in class. What are you thoughts on how to do it?
This is basically a new topic i know almost nothing about but i know basic formulas such as moles=mass/mr
n=v*c and q=mc▲t
we have done one lesson on calculating bond enthalpies knowing what exothermic and endothermic reactions are but that's about it so please walk me through how to do this. 
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 13032016 13:08
You have to use that equation q=mc▲t. You know C = 4.18, you convert degrees to Kelvin by adding 273 and your mass if the amount of CuSO4. (50cm3)
You get the answer and use the formula H= Q/mol
You work out the mol of CuSO4 and then you have the answer.
You have to divide the answer b y 1000 to get your final answer in KJ.
(I think that's how you do it but I might be wrong) 
thefatone
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 13032016 13:17
(Original post by yorobun)
You have to use that equation q=mc▲t. You know C = 4.18, you convert degrees to Kelvin by adding 273 and your mass if the amount of CuSO4. (50cm3)
You get the answer and use the formula H= Q/mol
You work out the mol of CuSO4 and then you have the answer.
You have to divide the answer b y 1000 to get your final answer in KJ.
(I think that's how you do it but I might be wrong)
This is a new formula what are the letter standing for? 
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 13032016 13:19
H is the enthalpy change, Q is the energy and mol is just moles.
You might need to change cm3 to dm3Last edited by yorobun; 13032016 at 13:20. 
thefatone
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 13032016 13:30
(Original post by yorobun)
You have to use that equation q=mc▲t. You know C = 4.18, you convert degrees to Kelvin by adding 273 and your mass if the amount of CuSO4. (50cm3)
You get the answer and use the formula H= Q/mol
You work out the mol of CuSO4 and then you have the answer.
You have to divide the answer b y 1000 to get your final answer in KJ.
(I think that's how you do it but I might be wrong) 
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 13032016 13:42
The mass you need for the equation is the mass of the surrounding, the surrounding is the CuSO4 so if you think about it like as if you were doing the experiment, you would pour the zinc powder in the solution of CuSO4 which is 50cm3 ( 0.05dm3). I get confused at this bit aswell but I remember doing a question and I had to use 100cm3 instead of actually working out the mass. Sorry if it doesn't make sense

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 13032016 13:46
(Original post by yorobun)
You have to use that equation q=mc▲t. You know C = 4.18, you convert degrees to Kelvin by adding 273 and your mass if the amount of CuSO4. (50cm3)
You get the answer and use the formula H= Q/mol
You work out the mol of CuSO4 and then you have the answer.
You have to divide the answer b y 1000 to get your final answer in KJ.
(I think that's how you do it but I might be wrong) 
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 13032016 13:47
(Original post by samb1234)
You don't need to convert temp to kelvin. Let x be initial temp in degrees C and y be end temp in degrees c, so delta T =yx. In kelvin, delta T =(y+273) (x+273) =yx 
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 13032016 13:48
(Original post by yorobun)
So its doesn't matter? Thankyou xD 
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 13032016 14:19
(Original post by thefatone)
Zinc will displace copper from copper (II) sulphate solution according to the following equation:
CuSO_{4}(aq) + Zn(s) > Cu(s) + ZnSO_{4}(aq)
Ifan excess of zinc powder is added to 50 cm^{3} of 1.0moldm^{3} copper(II) sulphate, the temperature increases by 6.3 ^{o}C. Calculate the enthalpy change for the reaction.
Assuming ρ =1.0 gcm^{3} and c = 4.18 Jg^{1}K^{1}
^{someone pls talk me through how to do this} 
thefatone
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 13032016 14:22
(Original post by yorobun)
The mass you need for the equation is the mass of the surrounding, the surrounding is the CuSO4 so if you think about it like as if you were doing the experiment, you would pour the zinc powder in the solution of CuSO4 which is 50cm3 ( 0.05dm3). I get confused at this bit aswell but I remember doing a question and I had to use 100cm3 instead of actually working out the mass. Sorry if it doesn't make sense
(Original post by samb1234)
Have you done this yet or do you still need help?
here's what i've done
n=(v*c)/1000
=0.05 mol of CuSO4
Mass=mol*mr
= 0.05*(63.5+32.1+16*4)
=7.98g
q=mc▲t
=7.98*4.18*6.3
=210.15J
h=q/mol
=210.15/0.05
=4202.9
4202.9/1000=4.203kJ/mol
of course 4.203kJ/mol bc this is an exothermic reaction
but this isn't the correct answer 
thefatone
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 13032016 14:26
(Original post by samb1234)
Have you done this yet or do you still need help? 
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 13032016 14:37
(Original post by thefatone)
Zinc will displace copper from copper (II) sulphate solution according to the following equation:
CuSO_{4}(aq) + Zn(s) > Cu(s) + ZnSO_{4}(aq)
Ifan excess of zinc powder is added to 50 cm^{3} of 1.0moldm^{3} copper(II) sulphate, the temperature increases by 6.3 ^{o}C. Calculate the enthalpy change for the reaction.
Assuming ρ =1.0 gcm^{3} and c = 4.18 Jg^{1}K^{1}
^{someone pls talk me through how to do this}
Step 2: We know that the unit for enthalpy change is KJ/mol , so we firstly need to go about changing our value from the first part into KJ by dividing by 1,000. We then calculate the number of moles of CuSO4 that reacted, and divide our energy change in KJ by the number of moles to get our final answer 
thefatone
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 13032016 14:52
(Original post by samb1234)
Step 1: we firstly need to work out what the energy change for the reaction is. We therefore can apply the formula Q=mc delta T. We know delta T, we are given c in the question but we now need to calculate the mass. The mass we use is the mass of the overall solution, and we are told in the question that the density of the solution is 1gcm3, so the overall mass of the solution is therefore 50g. We can then plug the numbers in to get a value for the energy released in J.
Step 2: We know that the unit for enthalpy change is KJ/mol , so we firstly need to go about changing our value from the first part into KJ by dividing by 1,000. We then calculate the number of moles of CuSO4 that reacted, and divide our energy change in KJ by the number of moles to get our final answer
In all the following questions, assume that thedensities and specific heat capacities of the solutions are the same as purewater i.e. ρ = 1.0 gcm^{3} and c = 4.18 Jg^{1}K^{1} 
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 13032016 14:58
(Original post by thefatone)
maybe i should've clarified
In all the following questions, assume that thedensities and specific heat capacities of the solutions are the same as purewater i.e. ρ = 1.0 gcm^{3} and c = 4.18 Jg^{1}K^{1} 
thefatone
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 13032016 15:04
(Original post by samb1234)
Step 1: we firstly need to work out what the energy change for the reaction is. We therefore can apply the formula Q=mc delta T. We know delta T, we are given c in the question but we now need to calculate the mass. The mass we use is the mass of the overall solution, and we are told in the question that the density of the solution is 1gcm3, so the overall mass of the solution is therefore 50g. We can then plug the numbers in to get a value for the energy released in J.
Step 2: We know that the unit for enthalpy change is KJ/mol , so we firstly need to go about changing our value from the first part into KJ by dividing by 1,000. We then calculate the number of moles of CuSO4 that reacted, and divide our energy change in KJ by the number of moles to get our final answer 
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 13032016 15:05
(Original post by thefatone)
How did you work that out? 
thefatone
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 13032016 15:12
(Original post by samb1234)
Denisty= mass/volume, so mass =volume x density
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Updated: March 13, 2016
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