Chemistry HW: What is the energy value of the olive oil in kJ/g?

Question

When a 0.560 g sample of olive oil is burned in a calorimeter, the heat released increases the temperature of 370 g of water from 22.7C to 39.1C. What is the energy value of the olive oil in kJ/g?

 

I need the answer in kJ and kcal. Also what equation would I be using for this question? Thank you in advanced!

Answer 1

The heat Q released by the burning oil must equal the heat that raised the temperature of the water.  

 

Q = mcΔT

 

m = mass of the WATER = 370 g = 0.370 kg

c = specific heat of WATER, which you can look up in your chemistry book, in appropriate units

ΔT = temperature rise of the water = (39.1 - 22.7)°C = ? °C

 

Plug the numbers into the equation for Q, and be careful working with units.  To get Q in kJ and kcal, you can look up c in kJ/(kg°C) and kcal/(kg°C).  Once you have Q, divide it by the mass of the oil to get the energy released in kJ/g of oil (or maybe kJ/kg and kcal/kg).

Answer 2

q = mCdT = (370g)(4.184J/g/deg)(16.4deg) = 25389J = 25.389 kJ. Since you have 0.560 g of oil, the energy per gram is 25.389 kJ/0.560g = 45.34 kJ/g = 45.3 kJ/g (to 3 sig figs)

1 cal = 4.184 j so hopefully you can convert to calories and kcal etc.