# Enthalpy change help!!

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#1
http://www.ocr.org.uk/Images/65360-q...-resources.pdf

Hi for 1ciiI) I have calculated the value of 11.495 KJ mol-1 but this not the not right answer as this is only the enthalpy change for 1 mole of NH4SCN. If you want to find the enthalpy change of formation, you need to * 11.495 by 2.

Q1: Why ? The question only asks for enthalpy change of formation, it doesn't specify which compound. 11.495 could be for Ba(OH)2 which is only 1 mole

Q2 I thought enthalpy change of formation to only to do with the product formed? No? Since only 1 mole of Ba(SCN)2 is formed why would you * by 2?

Q3 Could this also be the reaction of enthalpy change neutralisation ?

Thanks
0
3 years ago
#2
(Original post by coconut64)
http://www.ocr.org.uk/Images/65360-q...-resources.pdf

Hi for 1ciiI) I have calculated the value of 11.495 KJ mol-1 but this not the not right answer as this is only the enthalpy change for 1 mole of NH4SCN. If you want to find the enthalpy change of formation, you need to * 11.495 by 2.

Q1: Why ? The question only asks for enthalpy change of formation, it doesn't specify which compound. 11.495 could be for Ba(OH)2 which is only 1 mole

Q2 I thought enthalpy change of formation to only to do with the product formed? No? Since only 1 mole of Ba(SCN)2 is formed why would you * by 2?

Q3 Could this also be the reaction of enthalpy change neutralisation ?

Thanks
1.c(iii)

The formation of cyclohexanol from chlorocyclohexane involves the reaction of a nucleophile, the hydroxide ion.Suggest what feature of the hydroxide ion makes it able to act as a nucleophile.

???
0
#3
(Original post by charco)
1.c(iii)

The formation of cyclohexanol from chlorocyclohexane involves the reaction of a nucleophile, the hydroxide ion.Suggest what feature of the hydroxide ion makes it able to act as a nucleophile.

???
Sorry I meant 3biii). I am not sure why the answer should be* by 2 as enthalpy change of formation only applies to 1 mole. Thanks
0
3 years ago
#4
(Original post by coconut64)
Sorry I meant 3biii). I am not sure why the answer should be* by 2 as enthalpy change of formation only applies to 1 mole. Thanks
3b(iii) The enthalpy change of reaction is according to the balanced equation.

In 3b(ii) you calculate the energy change per mole of ammonium thiocyanate used, but there are two moles of thiocyanate in the balanced equation so you must multiply by 2
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