Chemistry: Calorimetry
Which units express specific heat capacity?
J/(gi°C), J/(giK), cal/(gi°C), cal/(giK)
calorie
a unit of energy equal to 4.18 J
Scientists are often interested in knowing the molar heat of combustion - the heat released during the combustion of one mole of a substance. Use the Periodic Table to find molar masses. How many moles of ethanol are present in the sample?
0.004993,.004993 mol
A sample of an unknown substance has a mass of 0.465 kg. If 3,000.0 J of heat is required to heat the substance from 50.0°C to 100.0°C, what is the specific heat of the substance?
0.129 J/(gi°C)
Which of the following has the smallest heat capacity?
3.0 g Pb
At what point will the heat flow stop?
When the temperatures of the cube and the container are equal.
Any heat lost by the metal is
gained by the calorimeter
As the temperature of a substance increases, the average kinetic energy of the particles in the substance...
increases
calorimetry
the use of a calorimeter to measure energy given off or absorbed during a physical or chemical process
The initial temperature of a bomb calorimeter is 28.50°C. When a chemist carries out a reaction in this calorimeter, its temperature decreases to 27.45°C. If the calorimeter has a mass of 1.400 kg and a specific heat of 3.52 J/(gi°C), how much heat is absorbed by the reaction?
5,170 J
A sample of ethanol (C2H6O) has a mass of 0.2301 g. Complete combustion of this sample causes the temperature of a bomb calorimeter to increase by 1.33°C. The calorimeter has a mass of 2.000 kg and a specific heat of 2.45 J/g•°C. What is the heat of combustion for this sample?
6.52 kJ
A cube of iron (Cp = 0.450 J/g•°C) with a mass of 55.8 g is heated from 25.0°C to 49.0°C. How much heat is required for this process? Round your answer to three significant figures.
603 J
The specific heat of water is 4.18 J/(gi°C) and that of wood is 1.97 J/(gi°C). Which statement is correct?
Given equal masses, water will heat up less than wood if the same heat is added.
Sodium carbonate (Na2CO3) reacts with acetic acid (CH3COOH) to form sodium acetate (NaCH3COO), carbon dioxide (CO2), and water (H2O). A chemist carries out this reaction in a bomb calorimeter. The reaction causes the temperature of a bomb calorimeter to decrease by 0.985 K. The calorimeter has a mass of 1.500 kg and a specific heat of 2.52 J/g•K. What is the heat of reaction for this system?
-3.72 kJ. This reaction is endothermic.
What is the molar heat of combustion for ethanol? Round using significant digits.
1,310 kJ/mol
Which of the following would release the most heat upon cooling from 75°C to 50°C?
10 g H₂O(I)
Which of the following has the most thermal energy?
15 L water at 25°C
A cube of aluminum (Cp = 0.897 J/g•K) has a temperature of 325 K. It is placed in a beaker of cold water. If the aluminum cools to 301 K as the water absorbs 815.7 J of heat, what is the mass of the cube?
37.9 g
When 40.0 mL of 1.00 M H2SO4 is added to 80.0 mL of 1.00 M NaOH at 20.00°C in a coffee cup calorimeter, the temperature of the aqueous solution increases to 29.20°C. If the mass of the solution is 120.0 g and the specific heat of the calorimeter and solution is 4.184 J/g • °C, how much heat is given off in the reaction? (Ignore the mass of the calorimeter in the calculation.)
4.62 kJ
A sample of tin (Cp = 0.227 J/g•°C) is placed in a freezer. Its temperature decreases from 15.0°C to −10.0°C as it releases 543 J of energy. What is the mass of the sample? Round your answer to three significant figures.
95.7 g
Which of the following shows the correct rearrangement of the the heat equation q = mCpΔT to solve for specific heat?
Cp=q/m∆T
A cube of copper has a temperature of 5°C. The cube is placed in a closed container whose internal temperature is 85°C. What will happen over time?
Heat will flow from the air in the container into the cube.
Which statement best describes why specific heat capacity is often more useful than heat capacity for scientists when comparing two materials?
Specific heat capacity is an intensive property and does not depend on sample size.
Which statement defines calorimeter?
a device that measures the heat that is gained or lost in a chemical change
calorimeter
a device used to measure the heat absorbed or evolved during a physical or chemical change
endothermic reaction
absorb energy
Bomb calorimeter
allows for determination of the heat of reaction
What would be the greatest difference in using an open ceramic coffee mug rather than an insulated mug with a lid as a calorimeter?
exchange of energy with the surroundings
exothermic reaction
releases energy
A sample of an unknown substance has a mass of 89.5 g. If 345.2 J of heat are required to heat the substance from 285 K to 305 K, what is the specific heat of the substance?
0.193 J/g∙K
The heat capacity of a sample should be divided by which quantity to find the specific heat capacity?
mass in grams
heat capacity
the quantity of heat needed to raise the temperature of a given sample of a substance by one degree Celsius (kelvin)
specific heat capacity
the quantity of heat required to raise the temperature of one gram of a substance by 1 degree Celsius (kelvin) at constant pressure
Which statement defines the heat capacity of a sample?
the quantity of heat that is required to raise 1 g of the sample by 1°C (or Kelvin) at a given pressure
The specific heat of water is 4.18 J/g•°C. How much heat does 225.0 g of water release when it cools from 85.5°C to 50.0°C? Enter your answer below, in whole numbers, without any commas.
33400
