2.1 g of a hydrocarbon fuel is burned in a calorimeter that contains 280 grams of water initially at 25.00◦c. after the combustion, the temperature is 26.55◦c. how much heat is evolved per gram of fuel burned? the heat capacity of the calorimeter (hardware only) is 92.3 j/◦c.

Explanation:

There are three heat transfers involved.

heat from combustion of propane + heat gained by water + heat gained by calorimeter = 0

  q₁     +     q₂      +       q₃      = 0

m₁ΔH + m₂C₂ΔT + C_calΔT = 0

Data:

 m₁ =      2.1   g

 m₂ = 280     g

   Ti = 25.00 °C

   T_f = 26.55 °C

Ccal = 92.3 J·°C⁻¹

Calculations:

Let's calculate the heats separately.

1. q₁

q₁ = 2.1 g × ΔH = 2.1ΔH g

2. q₂

ΔT = T_f - Ti = 26.55 °C - 25.00 °C = 1.55 °C

q₂ = 280 g × 4.184 J·°C⁻¹ × 1.55 °C = 1816 J

3. q₃

q₃ = 92.3 J·°C⁻¹ × 1.55 °C = 143.1 J

4. ΔH