Measurement of an enthaply change

Question 1

Describe a method to measure enthalpy change

Answer 1

Measure 25cm3 of 0.500moldm-3 hydrochloric acid into a polystyrene cup
Measure the temperature and record it in a table
Start the timer.
Record the temperature at 1 minutes, 2 minutes and 3 minutes
At the 4th minute, DO NOT record the temperature. Instead ADD 25cm3 of 0.500moldm-3 sodium hydroxide solution
Use a glass rod to stir
Record the temperature at 5 minutes and then at every minute until 10 minutes.

Question 2

Describe a graph of the analysis of enthalpy change

Answer 2

Temperature/°C against time/minutes
Points and line of best fit initially straight horizontal then shoot up.
Ignore anomalous points

Question 3

Equation for heat given out by neutralisation reaction

Answer 3

q=mcΔT

Question 4

Give equation for enthalpy change

Answer 4

ΔH=q/n

Question 5

Describe the combustion of a fuel in a spirit burner to increase temperature of a known volume of water.

Answer 5

Accurately weigh the mass of a spirit burner containing butan-1-ol and record it in a table
Measure 100.0cm’ of water into a beaker and place it above the spirit burner
Measure the temperature of the water and record it in a table
Light the wick of the spirit burner
allow the temperature of the water to rise approx. 20-25°C
Extinguish the spirt burner and record its mass in the table

Question 6

How to find mass of substance burned away

Answer 6

Inital mass of burner and substance-final mass of burner and substance

Question 7

Why is the world experiential values often inaccurate

Answer 7

Heat loss
Imcomplete combustion
Reaction unlikely to be under standard conditions

Question 8

How can the method be improved

Answer 8

Using a lid
Apply a stream of oxygen to the flame