IB DP Chemistry: SL復(fù)習(xí)筆記5.1.3 Calorimetry

Category: IB課程, 教材筆記, 福利干貨 Date: 2022年8月4日下午12:55

Calorimetry

Measuring enthalpy changes

Calorimetry?is a technique used to measure changes in enthalpy of chemical reactions
A?calorimeter?can be made up of a?polystyrene drinking cup, a?vacuum flask?or?metal can

1.5-Chemical-Energetics-Calorimeter

A polystyrene cup can act as a calorimeter to find enthalpy changes in a chemical reaction

The energy needed to raise the temperature of 1 g of a substance by 1 K is called the?specific heat capacity?(c) of the liquid
The?specific heat capacity?of water is 4.18 J g^-1?K^-1
The energy transferred as heat can be calculated by:

5.1.3-Calorimetry-variables-symbols_1

Equation for calculating energy transferred in a calorimeter

Worked Example

The energy from 0.01 mol of propan-1-ol was used to heat up 250 g of water. The temperature of the water rose from 298K to 310K (the specific heat capacity of water is 4.18 J g^-1?K^-1.Calculate the enthalpy of combustion.

Answer:

Step 1:?q = m x c x ΔT

m?(of water) = 250 g

c?(of water) = 4.18 J g^-1?K^-1

ΔT?(of water) = 310 - 298 K = 12 K

Step 2:?q = 250 x 4.18 x 12= 12 540 J

Step 3:? This is the energy released by 0.01 mol of propan-1-ol

Total energy? ? ΔH = q?÷ n = 12 540 J ÷ 0.01 mol = 1 254 000 J mol^-1

Total energy =?- 1254 kJ mol^-1