Chapter 14 - Energy changes in chemical reactions Flashcards

1
Q

What are exothermic reactions?

A

Reactions that release heat.

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2
Q

What are endothermic reactions?

A

Reactions that absorb heat

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3
Q

What is thermochemistry?

A

The study of energy changes in chemical reactions.

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4
Q

What is temperature?

A

The physical quantity we use to measure the degree of hotness or coldness of an object or substance.

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5
Q

What does specific heat capacity of a substance mean?

A

The amount of heat required to increase the temperature of unit mass of the substance by exactly 1C.

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6
Q

What is calorimetry?

A

The measurement and calculation of heat changes.

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7
Q

What formula is used to calculate the quantity of heat absorbed/released?

A

q=mc∆T

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8
Q

What does ∆T mean?

A

The change in temperature.

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8
Q

What does q mean in the q=mc∆T formula?

A

Quantity of heat absorbed.

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8
Q

How do we calculate heat released/absorbed per mole?

A

total heat release or absorbed/number of moles that reacted

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8
Q

What is enthalpy?

A

A measure of the total energy possessed by a substance or group of substances.

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9
Q

When a reaction is exothermic is ∆H positive or negative?

A

Negative.

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9
Q

What does c mean in the q=mc∆T formula?

A

The specific heat capacity.

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9
Q

What is the change in enthalpy for a chemical reaction ∆H mean?

A

The heat absorbed per mole of specified reactant or product when the reaction occurs at constant pressure.

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9
Q

When a reaction is endothermic is ∆H positive or negative?

A

Positive.

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9
Q

Is molar heat of combustion positive or negative?

A

Positive (because it releases heat).

10
Q

What is the molar enthalpy of solution/heat of solution?

A

The heat absorbed when one mole of the substance dissolves in a large excess of water.

10
Q

What is the law of conservation of energy?

A

Energy can be neither created nor destroyed but it can be changed from one form to another.

11
Q

What is ∆H sometimes referred to as?

A

The heat of reaction.

12
Q

What is dissociation?

A

Dissolving ionic substances in aqueous solution to form separated ions.

12
Q

What is the molar heat of combustion?

A

The heat liberated when 1 mole of the substance undergoes complete combustion with oxygen at a constant pressure of 100.0 kPa, with the final products being carbon dioxide gas and liquid water.

13
Q

What is an energy profile?

A

A diagram which shows the variation of the energy of a reacting system as a function of the progress of the reaction.

13
Q

Is the enthalpy change for a combustion process and enthalpy of combustion positive or negative?

A

Negative (because heat is absorbed).

13
Q

Do catalysts have any effect on the enthalpy change for the reaction?

A

No.