Question

Perform the following heat calculations. You must show all work and include units on answers.

The specific heat capacity of water is 4.184 J/g°C. How much heat is required to heat 500.0 g of water from 50.0°C to 100.°C?

A 45.4 g sample of lithium is cooled from 250.0°C to 25.0°C. The specific heat capacity of lithium is 3.56 J/g°C, what amount of heat is released?

Answer 1

Answer: 104600 Joules; 36365.4 Joules

Explanation:

A) For question 1

The quantity of Heat Energy (Q) required to heat a substance depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)

Thus, Q = MCΦ

Since, M = 500.0 g

C = 4.184 J/g°C

Φ = 100°C - 50°C = 50°C

Q = 500g x 4.184J/g°C x 50°C

Q= 104600 Joules

Thus, it takes 104600 Joules of heat energy to heat the water

B) For question 2

The quantity of Heat Energy (Q) released on cooling a heated substance depends on its Mass (M), specific heat capacity (C) and change in temperature (Φ)

Thus, Q = MCΦ

Since, M = 45.4 g

C = 3.56 J/g°C,

Φ = 250°C - 25°C = 225°C

Q = 45.4g x 3.56J/g°C x 225°C

Q= 36365.4 Joules

Thus, 36365.4 Joules of heat energy is released when the lithium is cooled.