RP2: Measuring Enthalpy Change Flashcards
1
Q
What is Hess’ Law?
A
The enthalpy change for a reaction is independent of the route taken.
2
Q
How can you reduce the uncertainty in the mass measurement?
A
Use a balance with a greater resolution and use a larger mass.
3
Q
What is percentage uncertainty and how do you calculate it?
A
% uncertainty = (actual/theoretical) x 100
4
Q
How do you calculate enthalpy change experimentally?
A
q = MCT
5
Q
Why may an experimental value for enthalpy change be different to the theoretical value?
A
- Heat loss to surroundings
- Incomplete combustion
- Non-standard conditions
- Evaporation of alcohol or water
6
Q
How do you prevent heat loss to surroundings?
A
- Insulate the beaker
- Avoid large temperature differences between surroundings
- Use a bomb calorimeter
7
Q
Other than preventing heat loss, how can the accuracy of this experiment be improved?
A
- Read the thermometer at eye level
- Stir the solution so the temperature is evenly distributed
- Use a digital thermometer for more accurate readings
- Use greater conc and masses = greater temp change
8
Q
What is accuracy?
A
The more accurate the data, the closer is it to the actual value.
