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Chemistry enthalpy help?

I have to work out the enthalpy changes of two reactions from an experiment, and I'm not sure how (my chemistry is quite weak- I'm working on it!!)

(Q=mct)??

The reactions are :

C6H8O7 (aq) + 3HCO-3(S) →C6H5O3-7(aq) + 3CO2 (g) + 3H2O (l)

[ Δ Temp = -16.00 oC

Volume = 25.00 cm^3

Mass = 8.40g ]


Cu2+ (aq) + Zn(s) →Cu(s) + Zn2+ (aq)

[Δ Temp = + 8.00 oC
Volume = 25.00cm^3
Mass = 0.63g ]


So how do I work out the enthalpy changes? Apparently I should work out the moles of the limiting reagent then the kJ mol -1 ?

Really confused, please help if you can

thanks!!!! :smile:
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Avatar for alow
alow
19
Original post by archie18
I have to work out the enthalpy changes of two reactions from an experiment, and I'm not sure how (my chemistry is quite weak- I'm working on it!!)

(Q=mct)??

The reactions are :

C6H8O7 (aq) + 3HCO-3(S) →C6H5O3-7(aq) + 3CO2 (g) + 3H2O (l)

[ Δ Temp = -16.00 oC

Volume = 25.00 cm^3

Mass = 8.40g ]


Cu2+ (aq) + Zn(s) →Cu(s) + Zn2+ (aq)

[Δ Temp = + 8.00 oC
Volume = 25.00cm^3
Mass = 0.63g ]


So how do I work out the enthalpy changes? Apparently I should work out the moles of the limiting reagent then the kJ mol -1 ?

Really confused, please help if you can

thanks!!!! :smile:


Use the mass of the liquids to find Q using the equation you posted. (1ml will be approximately 1g)

Then find the number moles of the limiting reagent and divide your energy change by this to get the enthalpy change.

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