Question 1

How would you purify a metal sulfide?

Accepted Answer

The answer of How would you purify a metal sulfide?
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Question 2

Sodium metal is ________.

Accepted Answer

The answer of Sodium metal is ________.
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Question 3

Iron is useful for reducing copper ions to copper metal. Might it also be used to reduce sodium ions to sodium metal?

Accepted Answer

Iron cannot be used to reduce sodium ions to sodium metal because sodium ions are more difficult to reduce compared to copper ions. This is due to the position of sodium in the electrochemical series, where it is much higher than iron, meaning it requires more energy to be reduced to its metallic form.

Question 4

Jewelry is often manufactured by electroplating an expensive metal such as gold over a cheaper metal. A setup for this process can be sketched as follows:  What would happen if the battery connections were suddenly reversed?

Accepted Answer

Reversing the battery connections would cause the current to flow in the opposite direction, which would cause the gold ions to be attracted to the gold electrode instead of the cheaper metal being electroplated. This would cause the gold ions to begin electroplating onto the gold electrode instead of the cheaper metal.

Question 5

A major source of chlorine gas,  , is from the electrolysis of brine, which is concentrated salt water,  What is the sign of the electrode where the chlorine gas is formed? Is it negative or positive?

Accepted Answer

The answer of A major source of chlorine gas, ...

Question 6

Metal ores are isolated from rock by taking advantage of differences in both physical and chemical properties. Cite examples given in the textbook where differences in physical properties are used.

Accepted Answer

The addition of oil to a slurry of metal sulfides (choice C) is an example of froth flotation, a process that exploits differences in the physical properties (specifically, surface properties) of minerals to separate valuable metal sulfides from less valuable minerals. This process does not involve changing the chemical composition of the substances involved, unlike electrolysis (choice A) and the addition of carbon in a blast furnace (choice B), which are chemical processes.

Question 7

How are most metals found in nature?

Accepted Answer

Most metals are found in nature as ionic compounds, typically combined with nonmetals in minerals.

Question 8

What is a drawback of roasting metal sulfides?

Accepted Answer

Roasting metal sulfides releases sulfur dioxide, a precursor to acid rain, and is energy-intensive. However, contamination with carbon is more associated with reduction processes involving carbon, not roasting.

Question 9

A major source of chlorine gas,  , is from the electrolysis of brine, which is concentrated salt water,  Which of the following is the balanced chemical reaction for this electrolysis reaction?

Accepted Answer

The answer of A major source of chlorine gas, ...

Question 10

How might electrolysis be used to raise the hull of a sunken ship?

Accepted Answer

The gaseous products of the electrolysis of water could be collected with large bags attached to the hull of the ship. As the bags inflate with the gas they are buoyed upward pulling the ship also upward. This is a practical option for using electrolysis to raise the hull of a sunken ship.

Question 11

What type of chemical reaction is involved in converting a metal salt into native metal?

Accepted Answer

Converting a metal salt into native metal involves the transfer of electrons from the metallic ion in the salt to another species, such as reducing agents like metal or hydrogen. This is a classic example of an oxidation-reduction reaction, also known as a redox reaction.

Question 12

Rust has a tendency to form when iron in contact with water reacts according to the following reaction: 4 Fe + 3 O₂ → 2 Fe₂O₃ _{What is happening at the cathodic region?}

Accepted Answer

The formation of rust involves the reduction of oxygen in the presence of water. Therefore, option C is correct. The cathodic region is where reduction occurs, and in this case, the oxygen is being reduced. The other options (A, B, and D) involve oxidation reactions, which occur at the anodic region.

Question 13

Which of the following metals would be the hardest to reduce to its native form from an ore?

Accepted Answer

Out of the given options, K (potassium) is the alkali metal with the lowest reduction potential. This means that it is highly reactive and has a strong tendency to oxidize, making it difficult to reduce from an ore to its native form. Additionally, potassium is not commonly found in its elemental form in nature, further complicating the reduction process. Therefore, potassium would be the hardest to reduce to its native form from an ore.

Question 14

Why is oxygen usually an oxidizing agent?

Accepted Answer

Oxygen has a high electronegativity, meaning it has a strong attraction for electrons. In chemical reactions, it tends to attract electrons away from other atoms or molecules, causing them to lose electrons and become oxidized. This makes oxygen a good oxidizing agent.

Question 15

During combustion, the oxygen atoms of oxygen molecules ________.

Accepted Answer

The answer of During combustion, the oxygen atoms of oxygen...

Question 16

In a metal-containing compound, the metal exists as a ________.

Accepted Answer

In a metal-containing compound, the metal typically exists as a positively charged ion, because metals tend to lose electrons and form cations when they combine with non-metals to form compounds.

Question 17

Which of the following metals would be the easiest to reduce to its native form from an ore?

Accepted Answer

Zinc has a lower reduction potential than the other metals listed, indicating that it requires less energy to remove an electron and reduce the metal ions to their native form.

Question 18

How does a blast furnace work?

Accepted Answer

A blast furnace works by adding a reductant (typically coke), which reacts with the oxygen atoms in the iron ore at high temperatures. This process reduces the iron ore to iron.

Question 19

The charge on the sulfur in the compound copper sulfide, Cu₂S, is ________.

Accepted Answer

The charge on copper is +2 (from its position on the periodic table), so the overall charge of the compound must be neutral. This means the total negative charge from sulfur must equal the total positive charge from copper. Since there is only one copper atom and one sulfur atom in the formula, the charge on sulfur must be -2 to balance out the +2 charge on copper.

Question 20

Why does a small amount of carbon strengthen iron?

Accepted Answer

Carbon atoms occupy interstitial sites in the iron lattice, creating a strain field that distorts the surrounding iron atoms. This distortion results in a decrease in the overall lattice parameter and an increase in the effective packing efficiency, which in turn leads to strengthening of the iron.

Quiz 11: Oxidations and Reductions Charge the World