Question 1

What would be the best explanation for the fact that most natural water has a pH of about 5.6?
A)Carbon dioxide reacts with water to form an acid.
B)Air contains acid rain particles.
C)Minerals that are dissolved in water are often acidic.
D)Many salts that dissolve in natural waters make the water basic.
E)none of the above

Accepted Answer

Carbon dioxide reacts with water to form carbonic acid, which has a pH of about 5.6. This is a common occurrence in natural water systems.

Question 2

How many electrons are gained or lost in the following half-reaction? Cl₂ → 2 Cl^- A)2 electrons are lost B)1/2 electron is gained C)1/2 electron is lost D)2 electrons are gained E)4 electrons are gained

Accepted Answer

The sulfur atom in Cl₂ has a formal charge of 0, and in Cl^- it has a formal charge of -2. This means that the sulfur atom has gained 2 electrons. Therefore, the half-reaction involves gaining 2 electrons, which corresponds to answer choice D.

Question 3

Why is carbon dioxide able to be stored more effectively in ocean water vs.fresh water? A)The pH of the ocean is pretty high and so the carbon dioxide is trapped in a neutralization reaction. B)The oceans are large and so you can dissolve more CO₂ in them. C)Gases are more soluble in cold water than warm water and the oceans are colder than fresh water lakes so you can dissolve more CO₂ in them. D)The pH of the ocean is very low and so the carbon dioxide is trapped as an acid because like dissolves like. E)none of the above

Accepted Answer

The answer of Why is carbon dioxide able to be...

Question 4

How many electrons are gained or lost in the following half-reaction? Zn → Zn⁺² A)2 electrons are lost B)1/2 electron is gained C)1/2 electron is lost D)2 electrons are gained E)4 electrons are gained

Accepted Answer

In the given half-reaction, Zn is transformed into Zn^2+, indicating that it loses 2 electrons to form a divalent cation. This is a typical oxidation process where the oxidation state of zinc increases from 0 in Zn to +2 in Zn^2+.

Question 5

How might you tell whether or not your toothpaste contained either calcium carbonate,CaC $\mathrm { O } _ { 3 }$ ,or baking soda,NaHC $\mathrm { O } _ { 3 }$ ,without looking at the ingredients label?
A)if the toothpaste bubbles when heated
B)if the toothpaste bubbles when added to ammonia,such as window cleaner
C)if the toothpaste produces a salt (NaCl)when added to HCl
D)if the toothpaste bubbles when added to vinegar

Accepted Answer

Calcium carbonate (CaCO3) and baking soda (NaHCO3) both react with acids to produce carbon dioxide gas, which causes bubbling. Vinegar is a common household acid that can be used for this test. Heating or adding to ammonia (a base) would not specifically indicate the presence of these compounds, and the production of a salt like NaCl from adding HCl doesn't uniquely identify these substances either, as many reactions with HCl can produce salts.

Question 6

What is oxidation?
A)the loss of electrons
B)the reaction with oxygen
C)the reduction of oxygen
D)the gaining of electrons
E)the addition of an electron to the valence shell

Accepted Answer

Oxidation is defined as the loss of electrons. This often occurs when a molecule or atom reacts with oxygen or loses electrons to another molecule. The opposite of oxidation is reduction, where a molecule or atom gains electrons.

Question 7

Which of the half-reactions below would be complementary,balance the following half-reaction,and be chemically reasonable? Br₂ → 2 Br^- A)2 K → 2 K⁺ B)K⁺ → K C)K → K⁺ D)2 K⁺ → 2 K E)K → K⁺²

Accepted Answer

The answer of Which of the half-reactions below would be...

Question 8

Which of the following statements is untrue about oxidation and reduction processes?
A)An oxidation can happen without a reduction.
B)It involves the exchange of electrons.
C)Often ions are generated or consumed.
D)Electrons are often involved in oxidation and reduction reactions.
E)All of the above are true.

Accepted Answer

Oxidation and reduction processes are complementary; an oxidation reaction occurs simultaneously with a reduction reaction in a redox process, involving the transfer of electrons from one substance to another. Therefore, an oxidation cannot happen without a corresponding reduction.

Question 9

Why might a small piece of chalk made of calcium carbonate be useful for alleviating acid indigestion?
A)Calcium carbonate is a base that reacts to neutralize any excess acids.
B)Calcium carbonate is able to absorb excess acid and carry it out of the system.
C)Calcium carbonate is able to add an extra lining to the stomach to protect it from the excess acid.
D)Calcium carbonate is able to turn the acid into a gas which can relieve the build up of excess acid.

Accepted Answer

Calcium carbonate is a base, which means it reacts with acids to neutralize them. So, when a small piece of chalk made of calcium carbonate is ingested, it reacts with any excess stomach acid and neutralizes it, providing relief from acid indigestion.

Question 10

How many electrons are gained or lost in the following half-reaction? Na → Na⁺ A)1 electron is lost B)1/2 electron is gained C)1/2 electron is lost D)1 electron is gained E)2 electrons are gained

Accepted Answer

In the half-reaction Na → Na^+, sodium loses one electron to form a sodium ion, Na^+. This is a process of oxidation, where an atom loses electrons.

Question 11

Lakes lying in granite basins,such as those in the northeastern U.S.,tend to become acidified by acid rain more readily than lakes lying in limestone basins,such as those found in the midwestern U.S.Why is this so?
A)The granite contains acidic minerals that dissolve in the rain water and are added to the lakes.
B)Since the acidified water cannot percolate through the granite,the acid in the lakes becomes more concentrated.
C)The limestone,which is calcium carbonate,serves to neutralize the acid in the rain.
D)There is more acid rain in the northeast than in the midwestern regions of the U.S.

Accepted Answer

Limestone, which is calcium carbonate, acts as a buffer and neutralizes the acid in the rain, helping to maintain a more neutral pH in the lakes. Granite, on the other hand, does not have this ability and can contribute to the acidification of the lakes. Therefore, lakes lying in granite basins tend to become acidified by acid rain more readily than lakes lying in limestone basins. Choices A and B are partially correct but do not explain the whole reason why lakes in granite basins are more susceptible to acid rain. Choice D is incorrect because acid rain affects both regions equally, but the geological composition of the basins plays a vital role in determining the susceptibility of the lakes to acidification.

Question 12

Pour vinegar onto beach sand from the Caribbean and the result is a lot of froth and bubbles.Pour vinegar onto beach sand from California,however,and nothing happens.Why?
A)Beaches in tropical climates generally have remnants of volcanic deposit not present in California sand.These deposits contain soil with organic residue.Vinegar's acetic acid reacts with organic matter.
B)The pH of the warm sands of tropical waters is well into the basic range,unlike the beach sand in California.Therefore,the acidic vinegar reacts with Caribbean beach sand but not with sand from California.
C)Beach sand from the Caribbean and many other tropical climates is made primarily of the calcium carbonate remains of coral and shelled creatures.Vinegar is an acid and the calcium carbonate is a base.
D)Caribbean beach sand contains deposits from the mouth of the Mississippi river which carries with it a great deal of contamination from urban waste.These warm water contaminates react with the acid in vinegar.

Accepted Answer

Beach sand from tropical climates, including the Caribbean, is primarily made of calcium carbonate remains of coral and shelled creatures. Vinegar is an acid and calcium carbonate is a base. Therefore, the reaction between the two causes the formation of bubbles and froth. California beach sand does not have the same composition and therefore does not react in the same way to vinegar.

Question 13

What happens to the pH of soda water as it loses its carbonation?
A)It does not change since the carbonation has nothing to do with pH.
B)It decreases as it loses the carbon dioxide molecules which form the carbonic acid in the soda.
C)It increases as it loses the carbon dioxide molecules which form the carbonic acid in the soda.
D)It decreases as the soda becomes more concentrated through the loss of the carbon dioxide gases.

Accepted Answer

When soda water loses its carbonation, the concentration of carbon dioxide decreases. This leads to a decrease in carbonic acid formation, making the solution less acidic and thus increasing the pH.

Question 14

Which of the half-reactions below would be complementary and balance the following half-reaction? Zn⁺² → Zn A)Cu → Cu⁺² B)K⁺ → K C)2 Cu → 2 Cu⁺² D)2 K⁺ → 2 K E)Cl₂ → 2 Cl^-

Accepted Answer

The answer of Which of the half-reactions below would be...

Question 15

Which of the following statements about oxidation and reduction reactions is true?
A)More than one electron can be transferred in an oxidation and reduction reaction.
B)In a half-reaction,only half of an electron is transferred.
C)Only neutral atoms are formed in oxidation and reduction reactions.
D)A half-reaction is only used for reduction reactions.
E)None of the above are true.

Accepted Answer

In oxidation and reduction reactions, more than one electron can be transferred. This can be seen in reactions like the reduction of oxygen in cellular respiration where 4 electrons are transferred to form water (O2 + 4e- + 4H+ → 2H2O).

Option B is incorrect because a half-reaction involves the transfer of a whole electron.

Option C is incorrect as oxidation and reduction reactions can result in the formation of ions such as in the reaction of sodium with chlorine to form sodium ions (Na+) and chloride ions (Cl-).

Option D is incorrect as half-reactions can be used for both oxidation and reduction reactions.

Question 16

Cutting back on the pollutants that cause acid rain is one solution to the problem of acidified lakes.Suggest another.
A)stop using NaCl to salt the roads in the winter
B)add a neutralizing substance such as limestone
C)add ammonium ions to the lakes
D)add chlorine and filter the water to remove any acidity in the lake

Accepted Answer

Adding a neutralizing substance such as limestone can help to counteract the effects of acid rain on lakes. Limestone contains calcium carbonate, which can react with acidic molecules in the water to form neutral compounds. This can help to raise the pH of the lake and reduce the harmful effects of acidification on aquatic life. The other options are not effective or could actually make the problem worse (e.g. adding ammonium ions would only increase the acidity of the lake).

Question 17

What is a reduction?
A)the gain of electrons
B)the reduction of the number of electrons
C)the loss of an electron from the valence shell
D)the reaction of oxygen with a reductant
E)the formation of red compounds in the presence of an oxidant

Accepted Answer

Reduction is the gain of electrons, which leads to a decrease in oxidation state.

Question 18

What is the source of acid rain? A)Acid rain is from dissolved carbon dioxide. B)All rain is acid rain because rain has a pH is less than 7. C)Rain is normally basic,but depending on the weather it can get slightly acidic. D)All rain is acid rain because rain has a hydronium ion concentration greater than 10^-7 M. E)none of the above

Accepted Answer

Acid rain is primarily caused by emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) which react with the water molecules in the atmosphere to produce acids. None of the options provided accurately describe this process.

Question 19

Why might an area with a large amount of limestone (CaCO₃)be less susceptible to acid rain? A)The acid in the rain is neutralized by the natural base in the limestone. B)The rain travels quickly through the porous limestone and therefore the rate of reaction is slower. C)Limestone is degraded by acid rain and therefore acid rain has the same damaging effects. D)Only acid rain made from sulfur compounds reacts with the limestone. E)none of the above

Accepted Answer

Limestone is a basic substance and therefore can neutralize acid. When acid rain falls on a surface with limestone, the limestone reacts with the acidic components, neutralizing them and preventing damage to the surface.

Question 20

How many electrons are gained or lost in the following half-reaction? 2 Na → 2 Na⁺ A)2 electrons are lost B)1/2 electron is gained C)1/2 electron is lost D)2 electrons are gained E)4 electrons are gained

Accepted Answer

In the given half-reaction, 2 Na atoms are transformed into 2 Na^+ ions, each losing 1 electron in the process, totaling 2 electrons lost.

Quiz 18: Two Classes of Chemical Reactions

What would be the best explanation for the fact that most natural water has a pH of about 5.6?

How many electrons are gained or lost in the following half-reaction? Cl₂ → 2 Cl^-

Why is carbon dioxide able to be stored more effectively in ocean water vs.fresh water?

How many electrons are gained or lost in the following half-reaction? Zn → Zn⁺²

How might you tell whether or not your toothpaste contained either calcium carbonate,CaC $\mathrm { O } _ { 3 }$ ,or baking soda,NaHC $\mathrm { O } _ { 3 }$ ,without looking at the ingredients label?

What is oxidation?

Which of the half-reactions below would be complementary,balance the following half-reaction,and be chemically reasonable? Br₂ → 2 Br^-

Which of the following statements is untrue about oxidation and reduction processes?

Why might a small piece of chalk made of calcium carbonate be useful for alleviating acid indigestion?

How many electrons are gained or lost in the following half-reaction? Na → Na⁺

Lakes lying in granite basins,such as those in the northeastern U.S.,tend to become acidified by acid rain more readily than lakes lying in limestone basins,such as those found in the midwestern U.S.Why is this so?

Pour vinegar onto beach sand from the Caribbean and the result is a lot of froth and bubbles.Pour vinegar onto beach sand from California,however,and nothing happens.Why?

What happens to the pH of soda water as it loses its carbonation?

Which of the half-reactions below would be complementary and balance the following half-reaction? Zn⁺² → Zn

Which of the following statements about oxidation and reduction reactions is true?

Cutting back on the pollutants that cause acid rain is one solution to the problem of acidified lakes.Suggest another.

What is a reduction?

What is the source of acid rain?

Why might an area with a large amount of limestone (CaCO₃) be less susceptible to acid rain?

How many electrons are gained or lost in the following half-reaction? 2 Na → 2 Na⁺