3.1.4.2 Calorimetry

Question 1

What is the equation involving heat gain/loss?

Answer 1

q = mcΔt

Question 2

What are the units of the specific heat capictity equation?

Answer 2

q - j
m - g
c - jg-1k-1
Δt - k

Question 3

What is a method for calorimetry?

Answer 3

1. Measure the mass of the spirit burner
2. Measurea fixed volume of H2O using a measuring cylinder
3. Place it in a test tube/beaker/calorimeter
   4.Insert the thermometer into the water and meaure the initial temperature
4. Ignite the spirit burner and measure the temperature change during a specific time
5. Measure the mass of theburner again
6. Calculate mass of fuel that is burnt
7. Use q = m x c x ΔT
8. Divide by the molof fuel burnt
9. Convert to KJ

Question 4

In a calorimetry experiment, 2.50 g of methane is burnt in excess oxygen.

30% of the energy released during the combustion is absorbed by 500 g of water, the temperature of which rises from 25 °C to 68 °C

The specific heat capacity of water is 4.18 J g-1 °C−1

What is the total energy released per gram of methane burnt?

Answer 4

Step 1: q = m x c x ΔT
m (of water) = 500 g
c (of water) = 4.18 J g-1 °C-1
ΔT (of water) = 68 oC - 25 oC
= 43 oC

Step 2: q = 500 x 4.18 x 43
= 89 870 J

Step 3: This is only 30% of the total energy released by methane
Total energy x 0.3 = 89 870 J
Total energy = 299 567 J
Step 4: This is released by 2.50 g of methane
Energy released by 1.00 g of methane = 299 567 ÷ 2.50
= 119 827 J = 120 000 J
= 120 kJ g-1