Thermochemistry

Thermochemistry

Solving Thermochemistry Problems

The steps you should follow to solve science word problems are below.

1. Identify the formula you should use.

2. Write the formula

3. Recognize the unknown. This will be in the form of a question. How much heat, or what was the initial temperature.

4. Identify the variables.

5. Substitute the values given into the formula.

6. Solve for the unknown.

Fill in the Blank

What unknown are you solving for in the problem below.

What mass of water would require 1025J of heat to raise the temperature from 17.5 degrees Celsius to 81.8 degrees Celsius?

Multiple Choice

What was the temperature change of 150g of water if it absorbed 8304J of heat?

• mass

• heat

• delta T

• specific heat

Next, identify the values given in the problems. The units provide a hint.

• q = heat, it will be measured in Joules or Calories

• m = mass, it will be measured in grams or Kilograms

• c = specific heat, it will be measured in J/g·ºC

• ΔT = change in temperature, it will be measured in °C. You may have to calculate this with the formula ΔT = Final temperature - initial temperature

Multiple Choice

Identify the variables in this problem.

Find the specific heat of a substance that releases 7852 J when 532g cools from 80°C to 70°C.

• q = 10°C, m = 532g

• q = 7852J, ΔT = 10°C

• q = 10°C, m = 532g, ΔT = 80°C

The cool thing is, this is the only formula you need!

q = mcΔT

Multiple Choice

Calculate the amount of heat needed to raise the temperature of 10g of aluminum from 100°C to 115°C. The specific heat of aluminum is 0.9025J/g·ºC.

• 135.38J

• -4513J

• 45.13J

• 45.13°C

Multiple Choice

How much heat is lost when 789g of acetic acid is cooled from 82.7°C to 25°C. The specific heat of the acid is 2.049J/g·°C.

• 1674.36J

• -1674.36J

• 3,731.25J

• -3731.25J

Multiple Choice

A piece of silver with a specific heat of 0.2165J/g·ºC cooled from 100.0ºC to 50.0ºC and released 875g of heat. What was the mass the silver?

• 50ºC

• 17.28g

• 17.5g

• 80.83g