Module 10

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

-2

Chemical equations need to be balanced not only in terms of the number of atoms, but also by the charge. In other words, just as there should be the same number of atoms before and after the arrow of an equation, there should be the same charge. What set of coefficients is necessary to balance the following chemical equation? ____ Sn2+ + ____ Ag → ____ Sn + ____ Ag⁺ 1, 1, 2, 1 1, 1, 1, 2 1, 2, 1, 2 1, 2, 2, 2

1, 2, 1, 2

In a battery, if the following oxidation-reduction reactions takes place normally: Mn2O3 + ZnO → 2 MnO2 + Zn What reaction would be taking place if you were charging the battery?

2 MnO2 + Zn → Mn2O3 + ZnO

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

2 electrons are gained

How many electrons are gained or lost in the following half-reaction? C → C4-

4 electrons are gained

Water is 88.88 percent oxygen by mass. Oxygen is exactly what a fire needs to grow brighter and stronger. Which of the following may be reasons why doesn't a fire grow brighter and stronger when water is added to it? All of the answers are correct. Oxygen in water is already "reduced" from the hydrogen atoms, so this oxygen atom no longer has a great attraction for additional electrons. The oxygen is chemically bound to hydrogen atoms and has different properties that elemental oxygen (O2). Oxygen in water is completely different from oxygen O2, which is what is required for combustion.

All of the answers are correct.

What might the relationship be between an element's electronegativity and its ability to behave as an oxidizing agent? As the electronegativity increases the ability of an element to act as an oxidizing agent decreases. As the electronegativity increases the ability of an element to act as an oxidizing agent increases. None of the answers are correct. As the electronegativity increases the ability of an element to act as an oxidizing agent stays the same.

As the electronegativity increases the ability of an element to act as an oxidizing agent increases.

A battery operates by ________. oxidation reduction Neither oxidation nor reduction. Both oxidation and reduction.

Both oxidation and reduction.

What is the primary difference between a fuel cell and a battery? Batteries can never be recharged, while fuel cells can be recharged. Fuel cells can continue to run as long as they are provided with a source of fuel; batteries run down and need to be recharged. Batteries supply electricity; fuel cells supply heat. Fuel cells oxidize to supply electricity, batteries reduce to supply electricity.

Fuel cells can continue to run as long as they are provided with a source of fuel; batteries run down and need to be recharged.

How would connecting iron with a wire to a piece of metal like copper, which undergoes reduction very easily, affect the rate at which the iron corrodes? It would increase the rate of corrosion. Rates are only affected by temperature. It would decrease the rate of corrosion. The rate would stay the same.

It would increase the rate of corrosion.

The general chemical equation for photosynthesis is shown below. Through this reaction is the carbon oxidized or reduced? How can you tell? 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Reduced, since in carbon dioxide there are two oxygen atoms for every one carbon but within the product, , (glucose), there is only one oxygen for every one carbon.

In the oxidation-reduction reaction Mg(s) + Cu2+(aq) → Mg2+(aq) + Cu(s), which atom or ion is reduced? Which atom or ion is oxidized? The Cu2+ ion is reduced as it gains electrons to form copper metal, Cu. The magnesium metal, Mg, is oxidized as it loses electrons to form Mg2+. Both the Cu2+ ion and the Mg are reduced in this reaction. The Cu2+ ion is oxidized as it gains electrons from the copper metal, Cu. The magnesium metal, Mg, is reduced as it loses electrons to form Mg2+. Both the Cu2+ ion and the Mg are oxidized in this reaction.

The Cu2+ ion is reduced as it gains electrons to form copper metal, Cu. The magnesium metal, Mg, is oxidized as it loses electrons to form Mg2+.

A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated salt water, At which electrode is the Cl2 formed? Neither the anode or the cathode. The anode since Cl- is being oxidized to Cl2. It could be formed at either the anode or the cathode. The cathode since Cl- is being oxidized to Cl2.

The anode since Cl- is being oxidized to Cl2.

The following set of redox reactions takes place as shown. Container A Container B Fe → Fe2+ + 2e- Cu2+ + 2e- → Cu If you had two containers filled with the ion solution described above with a wire connecting a piece of iron (in container A) and a piece of copper (in container B) and a salt-bridge connecting the two containers, which way do the positive ions in the salt-bridge flow? The ions only move in the containers they originate in. The positive ions flow back and forth between the two containers. The positive ions flow to container A. There is no flow of positive ions in the salt-bridge The positive ions flow to container B.

The positive ions flow to container B.

How does p-type silicon differ from pure silicon? There are no positive charges available. There are other elements with more valence electrons than silicon in the silicon matrix. There are other elements with less valence electrons than silicon in the silicon matrix. There are extra silicon atoms resulting in distortion of the silicon matrix.

There are other elements with less valence electrons than silicon in the silicon matrix.

The following set of redox reactions takes place as shown. Container A Container B Fe → Fe2+ + 2e- Cu2+ + 2e- → Cu If you had two containers filled with the ion solution described above with only a wire connecting a piece of iron (in container A) and a piece of copper (in container B), which way do the electrons flow?

There is no continuous flow of electrons without the presence of a salt bridge connecting the solutions in the two containers.

In the salt bridge, anions flow towards the ___________

anode

Oxidation will always occur at the _________ anode cathode

anode

Electrons will always flow from the __________ to the ____________ cathode anode

anode cathode

In a salt bridge, negative ions go to the oxidation side (__________), positive ions go to the reduction side (______________)

anode cathode

During combustion, the oxygen atoms of oxygen molecules ________.

become reduced

In the salt bridge, cations flow toward the _____________

cathode

Reduction always occurs at the____________ anode cathode

cathode

__________ __________ protecting a metal (like iron) from oxidation by placing it in electrical contact with a metal that has a greater tendency to oxidize.

cathodic protection

_________________________ is the study of the relationship between chemical reactions and electrical energy

electrochemsitry

___________ is the use of electrical energy to produce chemical change (the opposite of a voltaic cell)

electrolysis

______________ is the operation of coating one metal with another by electrolysis.

electroplating

_______ ________ is a device that converts energy of fuel to electrical energy

fuel cell

reduction= ____________ of electrons

gain

A ___________ reaction shows only the oxidation or the reduction reaction.

half

oxidation= ___________ of electrons

loss

When electrons are on the product side, they were given up or ________

lost

_______ type silicon contains extra electrons and have free negative charges

n type

Anions are ________ ions

negative

Oxidation state becomes more _____________ when it's gaining electrons.. This is called reduction/

negative

The ____________ terminal of a battery is where the electrons want to flow away from.

negative

Electrons have a negative charge so if something is gaining electrons, it will become more ___________. Which makes the oxidation state more ___________

negative negative

If something was reduced, it is the ___________ and considered as the __________ agent

oxidant oxidizing agent

The ionic state becomes more positive with _____________

oxidation

When the oxidation state becomes more positive, we know we've lost electrons and losing electrons is _____________

oxidation

If something is gaining oxygen, it is becoming ___________

oxidized

If something is losing hydrogen, its becoming ___________

oxidized

In oxidation reduction reactions- electrons flow from the reactant being ____________ to the reactant being ___________

oxidized reduced

_______ type silicon contains electron holes and any passing electron is attracted to this spot as if it were positively charged

p type

When boron is added to a layer of ultrapure silicon, the result is ________.

p-type silicon

The ___________ _____________ is the ability of light to excite electrons in an atom

photoelectric effect

_____________convert sunlight to electrical energy

photovoltaics

Cations are __________ ions

positive

Oxidation state becomes more ___________when it's losing electrons

positive

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

positively charged ion

A strong oxidizing agent means its easily ____________ and likes to gain electrons

reduced

If something is gaining hydrogen, it is becoming _____________

reduced

If something is losing oxygen, it is becoming ____________

reduced

It something is a strong oxidizing agent, it wants to be__________ and wants to _____________electrons.

reduced gain

If something was oxidized, it is the ___________ and considered as the ________________ agent

reductant reducing agent

The ionic state becomes more negative with ______________

reduction

When an oxidation state goes from 0 ---> -1, this is called ______________

reduction

In a battery, the following two oxidation-reduction reactions are taking place: rxn A: Zn → Zn2+ + 2e- rxn B: 2 NH4+ + 2e- → 2 NH3 + H2 Which reaction is taking place at the anode?

rxn A

____________ _____________ allow ions (separate from species involved in the reaction) to migrate between containers so no charge builds up in either container.

salt bridge

What is the purpose of a salt-bridge? to allow ions to migrate between solutions and maintain a charge balance to allow electrons to migrate through solutions All of the answers are correct. to allow salt to form in the oxidation-reduction reactions

to allow ions to migrate between solutions and maintain a charge balance

T or F: Both Corrosion and combustion utilize oxygen.

true

T or F: Combustion is happening in our body all the time as we metabolize food. It requires oxygen to combine with the food then produces glucose which we exhale and water.

true

T or F: Electrolysis can be used to break apart water or recharge batteries or purify metals

true

T or F: In Ionic compounds, elements have oxidation states equal to their ionic charges.

true

T or F: Ionic compounds like to be neutral

true

T or F: Metals in compounds always have a positive charge

true

T or F: On the left side of the equation, the coefficients nor the subscripts make a difference when determining the oxidation numbers.

true

T or F: Only a oxidation reduction reaction if it involves the transfer of electrons.

true

T or F: The oxidizing agent is something that is getting reduced.

true

T or F: To get metal atoms from a compound with a negative charge to a atoms with no charge, you will need to do an oxidization-reduction reaction and reduce the metal

true

T or F: When electrons are on the reactant side, they are being added (gained)

true

T or F: With an ionic compound, the oxidation states are equal to the charges of the ions in those compounds

true

__________ ______ chemical reaction that produces electricity

voltaic cell

Elements that are by themselves without a charge have an oxidation state of ___________

zero