Heat and Stoichiometry Flashcards

1
Q

True or False: heat is an intrinsic component of physical and chemical changes.

A

True

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2
Q

When heat must be added, meaning that the reaction requires energy, what is this process referred to as?

A

An endothermic reaction

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3
Q

Do physical and chemical changes involve energy changes as well?

A

Yes

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4
Q

When heat is lost, meaning that the reaction is releasing energy, what is this process referred to as?

A

An exothermic reaction

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5
Q

Energy can be released in what forms?

A

Sound, light, and heat

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6
Q

What is the reverse chemical reaction to combustion?

A

Electrolysis of liquid water to form hydrogen and oxygen

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7
Q

True or False: Energy can be viewed as either a reactant or a product in a chemical reaction

A

True

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8
Q

The amount of energy scales with what?

A

The amount of reactants used or products made

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9
Q

What is the definition of an endothermic reaction?

A

a reaction in which energy is absorbed from the surroundings

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10
Q

What is the definition of an exothermic reaction?

A

a reaction in which energy is released to the surroundings

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11
Q

When water is boiled and evaporated, heat must be added to the liquid water to form gaseous water this is a process of?

A

Endothermic reaction

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12
Q

When liquid water freezes to form ice, heat is lost during this process which makes this an example of?

A

Exothermic reactions

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13
Q

What is the SI unit of energy?

A

Joules (J)

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14
Q

True or False: Joules can be scaled up to kilojoules (kJ) just as we scale grams up to kilograms

A

True

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15
Q

What do we use joules and kilojoules for in a chemical reaction?

A

We use joules and kilojoules to quantify the energy involved in a chemical reaction similar to how we use moles and grams to quantify the reactants and products in a chemical reaction

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16
Q

When a reaction mixture’s temperature rises, this indicates?

A

An exothermic reaction because heat is the byproduct as the temperature is rising

17
Q

When a reaction mixture’s temperature drops, this indicates?

A

An endothermic reaction because heat is being absorbed which will not make it a product

18
Q

Which of the following are examples of endothermic reactions/processes?

A. Solid ammonium nitrate is added to a beaker of water. As it dissolves, the beaker feels cold.
B. When hydrogen gas and oxygen gas react to form water, a burst of flames is observed.
C. Solid sodium hydroxide pellets are added to a beaker of water. The beaker begins to feel warm to the touch.
D. Water is brought to a boil by placing a beaker of water onto a hot plate.

A

A- Heat is being absorbed meaning the energy will not be a product, therefore it will be a reactant
D- the water is boiling because it is absorbing the heat from the hot plate

19
Q

Which of the following are examples of exothermic reactions/processes?
A. Solid ammonium nitrate is added to a beaker of water. As it dissolves, the beaker feels cold.
B. When hydrogen gas and oxygen gas react to form water, a burst of flames is observed.
C. Solid sodium hydroxide pellets are added to a beaker of water. The beaker begins to feel warm to the touch.
D. Water is brought to a boil by placing a beaker of water onto a hot plate.

A

B- energy is being produced explicitly
C- The product of the beaker is heat after the pellets were added

20
Q

A reaction releasing or absorbing energy is the result of chemical bonds being broken and formed. As such, if one chemical bond being formed releases y amount of energy, how much energy would be released if 100 of these bonds were formed?

A

100y

21
Q

Using the following information, determine the amount of energy released when 0.835 g hydrogen gas is ignited in the presence of excess oxygen.

2 H2 (g) + O2 (g) → 2 H2O(g) + 483.6 kJ

A
  1. kJ