# chem question

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#1

how to calculate enthalpy change of reaction 3.1 from 3.2 and 3.3?
0
2 years ago
#2
reaction 3.1 = 3.2 - 2(3.3)

this is how you would get the overall equation for 3.1

u can find the enthalpy change of 3.2 by doing an experiment for Q=mcdeltaT

i think i've seen this q before, wasn't there more information and you had to work out Q for 3.2 first then find enthalpy change of 3.1 using the equation i wrote at the begiining
0
#3
(Original post by banter phalanx)
reaction 3.1 = 3.2 - 2(3.3)

this is how you would get the overall equation for 3.1

u can find the enthalpy change of 3.2 by doing an experiment for Q=mcdeltaT

i think i've seen this q before, wasn't there more information and you had to work out Q for 3.2 first then find enthalpy change of 3.1 using the equation i wrote at the begiining
yh i drew the hess cycle and i got the 3.2 value. But in the mark scheme they have multiplied the value of 3.3 by 2. why is this?
0
2 years ago
#4
(Original post by mansnothot)
yh i drew the hess cycle and i got the 3.2 value. But in the mark scheme they have multiplied the value of 3.3 by 2. why is this?
if you did the hess cycle correctly you would see that u need 2 x 3.3 to get your overall equation

u need 2 x HCl in the overall, u need 2NaOH to cancel out with 2NaOH from 3.2 etc

check your cycle again because so very clearly you need 2 x 3.3
1
#5
Can anyone help with this??
0
2 years ago
#6
Temperature decreases because the heat is spread over a larger volume of water
Enthalpy change of solution remains the same as the no. of moles isn't affected, as there was no change in mass
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