A container filled with 2.46 kg of water underwent a temperature change from 25.24 °C to 27.31 °C. How much heat, measured in kilojoules, did the water absorb?

The correct answer is 21.3 J

Explanation:

The heat absorbed by water can be calculated by using the following equation:

heat= m x Sh x ΔT

Where m is the mass of water (2.46 kg= 2460 g), Sh is the specific heat capacity of water (4.18 J/g.ºC) and ΔT is the difference of temperatures (final T - initial T). We introduce this values and calculate the heat:

heat=2460 g x 4.18 J/g.ºC x (27.31ºC - 25.24ºC)

heat= 21,285.39 J

As 1 KJ= 1000 J, we must divide the answer into 1000 to obtain the heat in KJ:

21,285.39 J x 1 KJ/1000 J= 21.28 KJ≅ 21.3 KJ

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%