required practical 2: measurement of enthalpy change

Question 1

formula for calorimetric enthalpy change (Q)

Answer 1

Q = m X C X ∆t
Q = energy change (J)
m = mass (g)
C = heat capacity
∆t = change in temp

Question 2

general method of calorimetry (solution and solid)

Answer 2

place polystyrene cup in glass beaker
measure desired volume of solution using volumetric pipette and transfer to cup
place thermometer in cup and measure initial temp
continue to measure temp at regular intervals until temp remains constant
if solid reactant is used - weigh before and after
stir mixture

Question 3

common errors during calorimetry experiments

Answer 3

heat energy lost to the surrounding
reaction may be incomplete
incomplete combustion - if fuel is used

Question 4

how can you improve the accuracy of this experiement

Answer 4

use electronic temperature sensor
use a flame calorimeter as less heat is lost

Question 5

why should glass beakers not be used during this experiment

Answer 5

glass is a poor conductor

Question 6

how is accuracy of this experiment improved

Answer 6

using insulators or lids to prevent heat loss

Question 7

how is the data from the method used to determine the temp change

Answer 7

record initial temp
record temp at regular intervals
plot graph - temp x time
extrapolate to point of addition
determine change in temp