Calorimetry

To know the amount of energy released three things must be known.
1) Temperature change (▲T) - measured with a thermometer
2) Amount of water (kg) ..... 1 g = 1 mL.... 1kg = 1000mL - measured with a scale
3) Specific heat capacity - how much heat a given substance can hold
water can hold 4.19 kj/kg °C

Equation
▲H= mC▲T
▲H= enthalpy change (kj)
m= mass of water (kj)
C = specific heat capacity (kg/kj °C)
▲T= change in temperature (°C)

Molar Enthalpy - Change in heat for each mole reacted

If you burn 0.315 moles of hexane (C₆H₁₄) in a bomb calorimeter containing 5.65 kg of water, what’s the molar heat of combustion of hexane is the water temperature rises 55.4⁰ C?

▲H = mC▲T

▲H = (5.65 kg)(4.19 kj/kg⁰C)(55.4⁰ C)

▲H = 1311.5 kJ

= 1312 kJ

If you burn 22.0 grams of propane (C₃H₈) in a bomb containing 3.25 kg of water, what’s the molar heat of combustion of propane if the water temperature rises 29.5⁰ C?

▲H = mC▲T

▲H = (3.25 kg)(4.19 kj/kg⁰C)(88.5⁰ C)

▲H = 1205.15 kj

▲H = 1205 kj

here is a quick worksheet to test your skills!

and here is a quick video that shows an experiment involving enthalphy. It is an exothermic reaction



and here is a how to video if youre still confused