Heat Capacity Example Problem - Find Final Temperature

How To Find the Final Temperature of a Reaction

Heating sample in lab
You can calculate final temperature based on initial temperature and energy. Romulic-Stojcic / Getty Images

This worked example problem demonstrates how to calculate the final temperature of a substance when given the amount of energy used, the mass and initial temperature.


300 grams of ethanol at 10 °C is heated with 14640 Joules of energy. What is the final temperature of the ethanol?

Useful information:
The specific heat of ethanol is 2.44 J/g·°C.


Use the formula

q = mcΔT

q = heat energy
m = mass
c = specific heat
ΔT = change in temperature

14640 J = (300 g)(2.44 J/g·°C)ΔT

Solve for ΔT:

ΔT = 14640 J/(300 g)(2.44 J/g·°C)
ΔT = 20 °C

ΔT = Tfinal - Tinitial
Tfinal = Tinital + ΔT
Tfinal = 10 °C + 20 °C
Tfinal = 30 °C


The final temperature of the ethanol is 30 °C.

Find Final Temperature After Mixing

When you mix together two substances with different initial temperatures, the same principles apply. If the materials don't chemically react, all you need to do to find the final temperature is to assume that both substances will eventually reach the same temperature. Here's an example:

Find the final temperature when 10.0 grams of aluminum at 130.0 °C mixes with 200.0 grams of water at 25 °C. Assume no water is lost as water vapor.

Again, you use:

q = mcΔT except since assume qaluminum = qwater, you are simply solving for T, which is the final temperature. You need to look up the specific heat values (c) for aluminum and water. I used 0.901 for aluminum and 4.18 for water.

(10)(130 - T)(0.901) = (200.0)(T - 25)(4.18)

T = 26.12 °C