Thermochemistry

How can the heat of reaction be determined from the standard heats of formation of the reactants and products?

• Add the standard heats of formation of the reactants and the products.

• Multiply the standard heats of formation of the reactants by that of the products.

• Subtract the standard heats of formation of the reactants from that of the products.

• Subtract the standard heats of formation of the products from that of the reactants.

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Is the flow of energy during vaporizing more like the flow of energy during melting or during freezing?

• It is more like the flow of energy during melting because both processes absorb energy.

• It is more like the flow of energy during freezing because both processes absorb energy.

• It is more like the flow of energy during melting because both processes release energy.

• It is more like the flow of energy during freezing because both processes release energy.

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A calorimeter holds 125 g water at 22.0°C. A 45 g sample of silver at 130.0°C is added to the water, and the final temperature of the water and silver is 24.2°C. The specific heat of water is 4.18 J/g°C. What is the specific heat of silver?

• 0.241 J/g°C

• 2.16 J/g°C

• 51.8 J/g°C

• 558 J/g°C

Tags

NGSS.HS-PS3-4

NGSS.HS-PS3-1

4.

What type of energy flows naturally from a hot object to a cooler object?

• potential energy

• light energy

• thermal energy

• mechanical energy

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How does an exothermic reaction compare with an endothermic reaction?

• Both changes absorb energy as reactants become products.

• Both changes release energy as reactants become products.

• An exothermic reaction absorbs energy, and an endothermic reaction releases energy.

• An endothermic reaction absorbs energy, and an exothermic reaction releases energy.

Tags

NGSS.HS-PS1-4

What happens to the surroundings when a substance freezes?

• The surroundings get cooler.

• The surroundings get warmer.

• The surroundings transfer thermal energy to the substance.

• The substance absorbs thermal energy from the surroundings.

7.

During which physical changes does a substance absorb energy from its surroundings?

• as it melts, freezes, and increases in temperature

• as it vaporizes, condenses, and decreases in temperature

• as it melts, vaporizes, and increases in temperature

• as it freezes, condenses, and decreases in temperature

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How does the flow of energy during freezing compare with the flow of energy during melting?

• In each process, energy flows into the material undergoing the change.

• In each process, energy flows out of the material undergoing the change.

• Energy flows into a substance that is freezing and out of a substance that is melting.

• Energy flows out of a substance that is freezing and into a substance that is melting.

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A hot piece of metal is placed into cooler water. Which statement describes how the second law of thermodynamics relates to this process?

• The temperature change of the metal is equal to the temperature change of the water.

• The amount of energy lost by the metal is equal to the amount of energy gained by the water.

• Energy flows from the metal to the water until they are at the same temperature.

• Energy flows from the water to the metal until they are at the same temperature.

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Which statement best describes the relationship between the system and the surroundings?

• The system is found in the surroundings but is not included as part of the surroundings.

• The system is found in the surroundings and is part of the surroundings.

• The system is found around the surroundings and includes the surroundings.

• The system is found around the surroundings but does not include the surroundings.