chem help plz!

When investigating the energy change betweent zinc and copper sulphate, does Hesse's law or enthalpy have anything to do with it? does anyone know the specific heat capacity of copper sulphate? And what are the factors affecting the energy change in this reaction? please help!

Reply 1

Willywonko

the_reason

When investigating the energy change betweent zinc and copper sulphate, does Hesse's law or enthalpy have anything to do with it? does anyone know the specific heat capacity of copper sulphate? And what are the factors affecting the energy change in this reaction? please help!

YOu have to be more specific; what is actually happening? are you adding solid zinc to aqueous copper sulphate, or what? And Hess' law seems very farfetched, that's not it.

Reply 2

the_reason

OP

I'm adding solid zinc into copper(II) suphate (aqeous solution). I am to investigate the energy change in the reaction.
What are the factors that affects the energy change?
and how do i convert temperature change into energy change?
Is this a exothermic or endothermic reaction?

Reply 3

WestSide

the_reason

I'm adding solid zinc into copper(II) suphate (aqeous solution). I am to investigate the energy change in the reaction.
What are the factors that affects the energy change?
and how do i convert temperature change into energy change?
Is this a exothermic or endothermic reaction?

Enthalpy change = Mass x Specific Heat Capacity x Temperature change

I think that's it, and you use the SHC of Water, and the mass of the CUSO4(aq). I apologise if this is wrong, as it seems so long since i completed my Chem A Level, even though it's only been a few months. :smile:

Reply 4

the_reason

OP

what r the factors?
Can someone explain what enthalpy is and how it is related to this experiment?

Reply 5

Gemza2

Enthalpy means energy, but i am not sure what experiment you mean?!! :confused:

Reply 6

the_reason

OP

Gemza2

Enthalpy means energy, but i am not sure what experiment you mean?!! :confused:

My experiment is to investigate a factor that affects the energy change in the reaction between zinc metal and aqueous solution of coppersulphate. now can sumone answer my question?

Reply 7

the_reason

OP

plz!i desperately need help!
u can PM me if you want

Reply 8

eurasianfeline

13

the_reason

When investigating the energy change betweent zinc and copper sulphate, does Hesse's law or enthalpy have anything to do with it? does anyone know the specific heat capacity of copper sulphate? And what are the factors affecting the energy change in this reaction? please help!

Did this prac last year...

Zn(s) + Cu2+(aq) --> Cu(s) + Zn2+ (aq)

Enthalpy change = energy change...but for A/S Chem you should always write Enthalpy change instead of Energy change

Basically, the point of doing this prac is to determine the enthalpy change for the above displacement rxn by measuring the temperature change over a period of time, and does not focus on Hess' Law. You are supposed to calculate the temperature change by plotting a graph of temperature vs time, and extrapolate the cooling curve back to the time when the Zn was added to find the MAX temp. rise (temp change = max - initial temp)

You do not need to know the SHC for CuSO4 because you can make the assumption that since it's in soln, thje SHC will be the same as water (4.18J/kg/K).

calculation: - delta H = mass(CuSO4) x SHC(water) x delta temp.

remember it's - delta H because it's an exothermic rxn

reason it is exothermic is because of the difference in reactivity between Cu & Zn, causing the displacement rxn (Zn replaces Cu)

hope it helps.

Reply 9

the_reason

OP

One more question...does anyone know how to calculate the amount of zinc i need when i am reacting it with 1M Copper(II)Sulphate for the reaction to have the precise amount of zinc needed to react fully with copper sulphate?
And what are the bond energies assosiated with it?

Reply 10

john !!

14

the_reason

One more question...does anyone know how to calculate the amount of zinc i need when i am reacting it with 1M Copper(II)Sulphate for the reaction to have the precise amount of zinc needed to react fully with copper sulphate?

Write a balanced equation for the reaction
look at how many moles of each you need
work out from this the number of zinc you need per mole of copper sulphate you have
(eg. if ratio is zinc:c.sulphate 3:2, you need 1.5 moles of zinc for every one mole of copper sulphate)

chose a volume of copper sulphate solution to use
use the equation moles = volume*concentration (in moles and dm^3) to work out the number of moles of copper sulphate ions you have (concentration is 1 M which you have said = 1 mol dm^-3)

now multiply the ratio you got before by the moles of copper sulphate you have to get the number of moles of zinc you need, and multiply this by the RMM of zinc to find the exact mass you need.

chem help plz!

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