RP2- Measuring Enthalpy Change Of A Reaction Flashcards
What reaction is used in this experiment?
Anhydrous copper (II) sulfate + water —> copper sulfate solution
Describe a method for measuring enthalpy change
Measure a specific mass of anhydrous copper (II) sulfate powder, and transfer to a dry stoppered test tube
Place 250cm3 of de-ionised water into an insulated polystyrene cup, start the stop watch and record the temperature every minute for three minutes
At minute four, add the anhydrous powder. Do not record the temperature at minute four
Record the temperature at minute five, and every minute after until minute 15
Plot a graph with temperature against time, draw two lines of best fit and extrapolate both lines
Use extrapolated lines to find the change in temperature at minute four
Once the temperature change at minute four is calculated, how can you calculate the enthalpy change?
Use equations
q= mc x change in T
Enthalpy change = q/n
What are the possible errors of this experiment?
Heat Energy can be lost to the surroundings
The method assumes that all solutions have the specific heat capacity of water
Incomplete reactions
The reaction may be too slow
The methods assumes that the density of all solutions is the same as water
Water may evaporate into surroundings
How can the experiment be made more accurate?
Use an electronic temperature sensor, and a data logging software to create a more precise graph
How can heat lost to the surroundings be minimised?
Cover the polystyrene/ insulated cup with a lid, after adding the powder rapidly
