Calorimetry

Calorimetry: An experimental method for finding enthalpy change by measuring temperature change over time. When observed and plotted on a graph, data can be extrapolated to give an accurate value for the change in temperature.

• 38 is the Tmax: the temperature before the reaction.

Calculating enthalpy change from experiments:

You will need to measure the following:

• The temperature of the water/solution before and after the experiment has concluded

• The mass of water/solution being heated

• This will be the same as volume as water/dilute solutions have a density of 1gcm^-3

• The moles of reactant (limiting) that reacts this may be calculated from:

  • The mass of a fuel burnt

  • The concentration/volume of a reactant

Enthalpy change calculation:

• Calculate the change in temperature

• Calculate the heat transferred using q=mc△T

  • q = heat transferred in J

  • m = mass of the water/solution being heated

  • c = specific heat capacity 4.2Jg^-1K^-1

  • △T = change in temperature

• When you know the heat transferred you need to calculate the moles that reacted

• Divide the value of q by the moles

• If the reaction was exothermic then make the value negative

• Remember to convert Jmol^-1 to kJmol^-1