1.4- energetics- thermochemistry

Question 1

what are the 2 different experiments to determine ΔH

Answer 1

1. reaction taking place in aqueous mixture- assume heat evolved by reaction is used to heat up the water in the mixture
2. determining enthalpy of combustion of a liquid using spirit burner- flame places under breaker of water- assume heat evolved by reaction is used to heat up the water in the mixture

Question 2

how to calculate heat given out/taken in during experiment

Answer 2

q=mcΔT
-q= heat change (J)
-m= mass of water (g)
-c= SHC of water (J g^-1 k^-1)
-ΔT= change in temp (K or degrees C)

Question 3

how to calculate enthalpy change in kJmol^-1

Answer 3

ΔH= - q
——————
moles x 1000

Question 4

things to remember when calculating enthalpy change

Answer 4

if temp change is positive, ΔH will be negative
if temp change is negative, ΔH will be positive