Question

When 20 g of a fuel is burnt, the heat released raises the temperature of 200 g of water by 5 0C, what is the enthalpy of combustion of the fuel in kJ/g? (cwater = 4.184 Jg-1K -1 )

Answer 1

The enthalpy of combustion of the fuel is calculated by determining the amount of heat absorbed by the water, which is 4.184 kJ. This heat is released by burning 20 g of fuel, leading to an enthalpy of combustion of 0.2092 kJ/g for the fuel.

Step-by-step explanation:

To calculate the enthalpy of combustion of the fuel in kJ/g, we can use the information given about the temperature rise of water when the fuel is burned. The formula to find the amount of heat (q) absorbed by the water is q = mass × specific heat capacity × temperature change. Applying the data given:

• 
  
• mass of water (mwater) = 200 g
• 
  
• specific heat capacity of water (cwater) = 4.184 J/g°C
• 
  
• temperature change (ΔT) = 5 °C

The amount of heat absorbed by the water when the fuel is burned is:

qwater = mwater × cwater × ΔT

= 200 g × 4.184 J/g°C × 5 °C

= 4184 J

= 4.184 kJ

The fuel's mass is 20 g, so the enthalpy of combustion per gram of fuel is:

ΔHcombustion = qwater / mass of fuel

= 4.184 kJ / 20 g

= 0.2092 kJ/g

This value represents the amount of heat released per gram of the fuel when it is burnt.