Question

5

How many J of energy are needed to raise the temperature of 18.3 g of
water from 11.88°C to 49.32°C?*
2540 J
1740 J
2870 J
3570 J

Answer 1

Q = mcΔT, where Q is the heat energy, m is the mass, c is the specific heat, and ΔT is the change in temperature (T₂-T₁). The specific heat of water is 4.184 J/g °C. We are given the mass of water (m = 18.3 g), the final temperature (T₂ = 49.32 °C), and the initial temperature (T₁ = 11.88 °C). The change in temperature, ΔT, equals 49.32 °C - 11.88 °C = 37.44 °C. With all these values at hand, we can solve for the amount of energy needed, Q:

Q = (18.3 g)(4.184 J/g °C)(37.44 °C) = 2866.7 J ≈ 2870 J (three sig figs).