Multiple Choice
Two compounds were dissolved in water and mixed together. A precipitate formed, and the test tube got very warm. Based on this information, which of these statements is true?
8. Thermochemistry
Endothermic & Exothermic Reactions
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A 25.0 g piece of aluminum (which has a molar heat capacity of 24.03 J/mol °C) is heated to 85.1 °C and dropped into a calorimeter containing water (specific heat capacity of water is 4.18 J/g °C) initially at 25.0 °C. Assuming no heat is lost to the surroundings, what is the final temperature of the system?
A
35.0 °C
B
30.0 °C
C
32.5 °C
D
27.5 °C
Verified step by step guidance1
First, identify the key components of the problem: the aluminum piece and the water in the calorimeter. We need to find the final temperature of the system when they reach thermal equilibrium.
Calculate the heat lost by the aluminum as it cools down. Use the formula: , where is the mass of aluminum, is the molar heat capacity, and is the change in temperature.
Convert the mass of aluminum from grams to moles using its molar mass (approximately 26.98 g/mol). This will allow you to use the molar heat capacity in the calculation.
Calculate the heat gained by the water as it warms up. Use the formula: , where is the mass of water, is the specific heat capacity, and is the change in temperature.
Set the heat lost by aluminum equal to the heat gained by water, since no heat is lost to the surroundings. Solve for the final temperature of the system, , using the equation: .
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