MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Given the reaction:

S(s)+ O₂ (g) -->SO₂ (g) + energy

Which diagram best represents the potential energy changes for this reaction?

a. top left

b. top right

c. bottom left

d. .bottom right

Correct Answer: a

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

An oxidation-reduction reaction is set up so that both half-reactions take place in separate beakers that are connected by a salt bridge and an external conductor. A path for the transfer of ions is provided by the

a. anode

b. cathode

c. salt bridge

d. external conductor

Correct Answer: c

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

An oxidation half-reaction always involves the

a. gain of electrons

b. gain of protons

c. loss of electrons

d. loss of protons

Correct Answer: c

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Given the electrochemical cell reaction:

Zn(s) + Ni²(aq) --> Zn²⁺(aq) + Ni(s)

Which species is oxidized?

a. Zn

b. Ni²⁺

c. Zn²⁺

d. Ni

Correct Answer: a

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

As an electrochemical cell approaches equilibrium, the electrical energy supplied by the cell

a. decreases

b. increases

c. remains the same

Correct Answer: a

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Which component of an electrochemical cell is correctly paired with its function?

a. external conductorÑallows the solutions to mix

b. external conductorÑpermits the migration of ions

c. salt bridgeÑallows the solutions to mix

d. salt bridgeÑpermits the migration of ions

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Magnesium reacts with oxygen to form magnesium oxide according to the following equation:

2Mg_(s) + O_2(g) Í 2MGO_(S)

If 0.81 grams of magnesium oxide are formed, how many grams of oxygen reacted?

a. .020 grams 02

b. .025 grams 02

c. .81 grams 02

d. .0 10 grams 02

e. 0.40 grams 02

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Use the following equation to answer the question:

Energy + 2C + 3H₂ C₂H₆

carbon hydrogen ethane

On the right hand side of the equation are two carbons and six hydrogens. On the left hand side are two carbons and six hydrogens. This is because:

a. Only two carbons can react with six hydrogens.

b. The conservation of matter is reflected in this model.

c. The conservation of volume is reflected in this model.

d. The formation of ethane requires small amounts of energy.

e. The formation of ethane requires large amounts of energy.

Correct Answer: b

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Given the equation:

H₂(g) + Cl₂(g) --> 2HCl(g)

What is the total number of moles of HCl(g) produced when 3 moles of H₂(g) is completely consumed?

a. 5 moles

b. 2 moles

c. 3 moles

d. 6 moles

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Salt A and salt B were each dissolved in separate beakers of water at 21¡C. The temperature of the salt A solution decrease, and the temperature of the sat B solution increased. Based on these results, which conclusion is correct?

a. The water gained energy from both salt A and salt B.

b. The water lost energy to both salt A and salt B.

c. The water gained energy from salt A and lost energy to salt B.

d. The water lost energy to salt A and gained energy from salt B.

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Which phase change is accompanied by the release of heat?

a. H₂O(s) --> H₂O(g)

b. H₂O(s) --> H₂O(l)

c. H₂O(l) --> H₂O(g)

d. H₂O(l) --> H₂O(s)

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Given the reaction:

H₂O (l) + 68.3 kcal H₂(g) + 1/2 O₂(g)

Which statement describes the reverse reaction?

a. It is endothermic and releases energy.

b. It is endothermic and absorbs energy.

c. It is exothermic and releases energy.

d. It is exothermic and absorbs energy.

Correct Answer: c

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

The burning of magnesium involves a conversion of

a. chemical energy to mechanical energy

b. chemical energy to heat energy

c. heat energy to chemical energy

d. heat energy to mechanical energy

Correct Answer: b

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

The burning of a match is common example of a chemical reaction. What happens to most of the energy in the match when it burns?

a. It is transformed into the potential energy of heat and light

b. It is transformed into carbon dioxide and water

c. It is transformed into ash and smoke

d. It is transformed into kinetic energy of heat and light

e. There is no change in the forms of energy

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

A student makes the following measurements in the process of reacting 20 mL of solution A and 20 ml, of solution B.

Initial temp of solution A	Initial temp of solution B	Temp of mixture at time = 0	Temp of mixture at time = 1 min	Temp of mixture at time = 2 min	Temp of mixture at time = 3 min	Temp of mixture at time = 4 min
22 ≈C	22 ≈C	26 ¡C	25 ¡C	24 ¡C	23 ¡C	22 ¡C

How would you classify this reaction in terms of the energy change?

a. The reaction is endothermic because the temperature drops.

b. The reaction is neither endothermic nor exothermic because the temperature returns to 22¡C.

c. The reaction is endothermic because the temperature rises.

d. The reaction is exothermic because the temperature rises.

e. The reaction is exothermic because the temperature drops.

Correct Answer: d

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

1. Which term describes a reaction in which heat is part of the product?

a. cosmothermic

b. endothermic

c. exothermic

d. isothermic

e. nonthermic

2. Which term describes a reaction in which heat is part of the reactants?

a. cosmothermic

b. endothermic

c. exothermic

d. isothermic

e. nonthermic

Correct Answers:

1. c

2. b

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

A student observed that when sodium hydroxide was dissolved in water, the temperature of the water increased. The student should conclude that the dissolving of sodium hydroxide

a. is endothermic

b. is exothermic

c. produces an acid solution

d. produces a salt solution

Correct Answer: b

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

When ammonium chloride crystals are dissolved in water, the temperature of the water decreases. What does the temperature change indicate about the dissolving of ammonium chloride in water?

a. It is an endothermic reaction because it absorbs heat.

b. It is an endothermic reaction because it releases heat.

c. It is an exothermic reaction because it absorbs heat.

d. It is an exothermic reaction because it releases heat.

Correct Answer: a

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Which phase change is exothermic?

a. solid to liquid

b. solid to gas

c. liquid to solid

d. liquid to gas

Correct Answer: c

MC	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Which statement correctly describes this reaction?

a. It is endothermic and energy is absorbed.

b. It is endothermic and energy is released.

c. It is exothermic and energy is absorbed.

d. It is exothermic and energy is released.

Correct Answer: d

I	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO:

Answer the following questions:

1. Using a jar with a tight fitting lid, a student mixes 2.00 grams of calcium metal and 100 ml of water; the lid is placed on the bottle. The calcium dissolves and gas bubbles rise to the surface of the liquid. What do you predict has happened to the mass of the of the material inside the jar?

a. The mass has decreased.

b. The mass has increased.

c. The mass has not changed.

d. The mass is now 98 grams.

e. The mass is now 100 grams.

2. Using a container that will seal so that no gas can escape, as student places 5.00 grams of calcium metal and 150 ml of hydrochloric acid. The metal dissolves and gas bubbles rise to the surface of the liquid. What do you predict has happened to the mass of the material inside the container?

a. The mass is 145 grams.

b. The mass is 155 grams.

c. The mass has decreased.

d. The mass has increased.

e. The mass has not changed.

Correct Answer:

1. c

2. e

I	Chemistry	Standard: 04
Objective: 02. Analyze evidence for conservation of mass and energy in chemical reactions.
ILO: