Thermochemical/calibration

Question 1

Endothermic vs Exothermic

Answer 1

Exothermic:
- Releases energy into the environment
- Energy of products is less (more stable)

Endothermic:
- Absorbs energy from the environment
- Energy of products is more (less stable)

Question 2

Combustion reaction

Answer 2

• Exothermic
• requires 3 things
  1. Fuel to burn
  2. Oxygen to react with
  3. Energy to start the process

Complete: H2O + CO2

Incomplete: CO/C/CO2 (question will tell you)

Question 3

Enthalpy

Answer 3

• Enthalpy (H) is the total heat content of a system at constant pressure.
• Enthalpy change (ΔH) indicates whether a reaction absorbs or releases heat.
• Energy released = n(mol) x ΔH
• CHANGING STATES effects ΔH

Question 4

Experiments to determine ΔH

Answer 4

Calorimetry
1. wick and water
2. Bomb calorimetry
3. Solution Calorimetry

Question 5

Wick and water

Answer 5

• q = mcΔt
• ΔH = q/n (energy per mol)

Errors:
- Heat loss
- Impuritities in fuel
- Doesn’t use electricla heating to counteract heat loss

Question 6

Bomb calorimetry

Answer 6

• Sealed bomb vessel, to try negate most heat loss
• Gaseous reactant

Question 7

Solution calorimetry

Answer 7

• The insulated cup prevents transfer of heat into the surroundings
• Not always 100% percent effective the container can absorb heat

Question 8

Calibration

Answer 8

Electrical calibration:
- E = VIt (volt x current x time)
- CF = E/Δt

Chemical calibration:
- q = nΔH
- CF = q/Δt