Oxidation-Reduction Reactions - Organic Chemistry
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The oxidation numbers of calcium and chromium in the compound 
are __________ and __________, respectively.
The oxidation numbers of calcium and chromium in the compound
Calcium is in the second group of the periodic table, so its oxidation number will always be 
. This is true for all alkaline earth metals.
As for chromium, the dichromate anion (
) has an overall charge of 
. Each oxygen atom will always have an oxidation number of 
as well, so the oxygens would have a total negative charge of 
. The sum of the oxidation numbers have to equal the overall charge, so chromium must be used to balance the negative charges from the oxygen. To bring the overall charge to 
, the two chromiums have to have total charge of 
, giving each an oxidation number of 
.
Calcium is in the second group of the periodic table, so its oxidation number will always be
As for chromium, the dichromate anion (
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What is the oxidation number of the manganese in potassium permanganate?
What is the oxidation number of the manganese in potassium permanganate?
Manganese is a transition metal, so its oxidation number is more variable than the other elements of the compound. Oxygen is almost always 
. Potassium is almost always 
. The sum of the oxygens and the potassium is 
.
The compound is neutral, so the manganese is 
to balance the net molecular charge.
Manganese is a transition metal, so its oxidation number is more variable than the other elements of the compound. Oxygen is almost always
The compound is neutral, so the manganese is
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Compared to oxygen in water, the oxygen in hydrogen peroxide has __________ valence electron(s).
Compared to oxygen in water, the oxygen in hydrogen peroxide has __________ valence electron(s).
To solve this question we need to calculate the oxidation number of oxygen in both molecules. The formula for water is 
. The oxidation number of hydrogen is +1. Since there are two of them, the hydrogen atoms contribute to a charge of +2. The water molecule is neutral; therefore, the oxygen must have an oxidation number of 
to balance the charge. The formula for hydrogen peroxide is 
. Using the same logic as water, we can determine that hydrogen contributes +2. We have two oxygen atoms in this case; therefore, each oxygen atom will have an oxidation number of 
to give a charge of 
. This will balance the charges and provide a neutral hydrogen peroxide molecule.
Recall that have a negative charge suggests that an atom has extra valence electrons. A charge of 
suggests one extra valence electron and a charge of 
suggests two extra valence electrons. An oxygen typically has six valence electrons. The oxygen in water has 
oxidation number; therefore, it will have two extra valence electrons (eight total). On the other hand, oxygen in hydrogen peroxide will have one extra valence electron (seven total); therefore, oxygen in hydrogen peroxide has one less valence electron than oxygen in water.
To solve this question we need to calculate the oxidation number of oxygen in both molecules. The formula for water is
Recall that have a negative charge suggests that an atom has extra valence electrons. A charge of
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Which of the following is true regarding the correct oxidation number of potassium in potassium bromide?
Which of the following is true regarding the correct oxidation number of potassium in potassium bromide?
Potassium bromide has a formula of 
. This molecule is made up of an alkali metal (potassium) and a halogen (bromine). Alkali metals have one valence electron that they readily lose to obtain octet whereas halogens have seven valence electrons and they readily gain an electron to obtain octet. Recall that losing an electron will give you a 
oxidation number whereas gaining an electron will give you a 
oxidation number. This means that alkali metals always have an oxidation number of 
whereas halogens always have an oxidation number of 
; therefore, potassium has an oxidation number of 
.
Potassium bromide has a formula of
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A student reacts sodium chloride and lithium bromide. He collects the products in a jar and performs several tests on them. He concludes that product A has a metal and a nonmetal and that the metal has an oxidation number of 
whereas the nonmetal has an oxidation number of 
. What can you conclude from these results?
A student reacts sodium chloride and lithium bromide. He collects the products in a jar and performs several tests on them. He concludes that product A has a metal and a nonmetal and that the metal has an oxidation number of
The reaction stated in this question is as follows.
This is a double replacement reaction. Both products contain a metal (an alkali metal) and a nonmetal (a halogen). The oxidation number of all alkali metals (first column of periodic table) is 
and of all halogens (seventh column of periodic table) is 
. The results stated in the question seem invalid because a halogen can never have an oxidation number of 
.
The reaction stated in this question is as follows.
This is a double replacement reaction. Both products contain a metal (an alkali metal) and a nonmetal (a halogen). The oxidation number of all alkali metals (first column of periodic table) is
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Which of the following is the correct oxidation number of manganese in Manganese(III) oxide?
Which of the following is the correct oxidation number of manganese in Manganese(III) oxide?
Manganese(III) oxide has a formula of 
. The oxidation number of oxygen is 
. Since there are three of them, the oxygen atoms contribute to a charge of 
. To maintain the neutrality of the molecule, manganese must balance the 
charge (meaning contribute 
charge). There are two manganese atoms; therefore, each manganese atom will have an oxidation number of 
and contribute 
charge.
Manganese(III) oxide has a formula of
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In the compound 
, what is the oxidation number of 
?
In the compound
Generally, oxygen has an oxidation number of 
, and hydrogen has an oxidation number of 
. If we multiply 
by the number of oxygen atoms in the compound (
), we get an overall charge of 
on the oxygen. If we multiply 
by the number of hydrogen atoms in the compound (
), we get an overall charge of 
on the hydrogen. The sum of 
and 
is 
. We can see that 
is a neutral molecule, so the charge on 
would have to balance out the 
charge on the rest of the molecule. To obtain a charge of 
, the oxidation number on 
must then be 
.
Generally, oxygen has an oxidation number of
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Which of the following is NOT an oxidizing agent?
Which of the following is NOT an oxidizing agent?
The answer is 
.
Lindlar's catalyst enables catalytic hydrogenation, specifically for an alkyne to reduce to a cis-alkene (though the reaction does not continue to produce an alkane). The rest of the answer options are oxidizing agents.
The answer is
Lindlar's catalyst enables catalytic hydrogenation, specifically for an alkyne to reduce to a cis-alkene (though the reaction does not continue to produce an alkane). The rest of the answer options are oxidizing agents.
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A water molecule is converted to hydrogen peroxide through a series of reactions. What can you conclude about the oxygen molecule?
A water molecule is converted to hydrogen peroxide through a series of reactions. What can you conclude about the oxygen molecule?
Water, 
, has an oxygen atom with an oxidation number of 
whereas hydrogen peroxide, 
, has an oxygen atom with an oxidation number of 
. A less negative oxidation number suggests that the oxygen lost an electron. Recall that oxidation is the loss of electrons whereas reduction is the gain of electrons; therefore, the oxygen atom lost an electron and was oxidized when water was converted to hydrogen peroxide.
Water,
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Which of the following is true regarding oxidation?
I. Oxidation increases the oxidation number
II. Oxidizing agent is always reduced
III. Oxidation of an atom is always spontaneous
Which of the following is true regarding oxidation?
I. Oxidation increases the oxidation number
II. Oxidizing agent is always reduced
III. Oxidation of an atom is always spontaneous
Oxidation is the process of removing electrons from an atom. This increases the oxidation number (makes oxidation number more positive). An atom undergoes oxidation by losing electrons and donating them to another atom. Since it is facilitating reduction (gain of electrons) of another atom, an atom that is oxidized is also called a reducing agent. Oxidizing agents, on the other hand, are reduced (gain electrons) and facilitate the oxidation of other atoms (removal of electrons from other atoms). Oxidation of an atom does not depend on the Gibbs free energy; therefore, oxidation can be spontaneous or nonspontaneous.
Oxidation is the process of removing electrons from an atom. This increases the oxidation number (makes oxidation number more positive). An atom undergoes oxidation by losing electrons and donating them to another atom. Since it is facilitating reduction (gain of electrons) of another atom, an atom that is oxidized is also called a reducing agent. Oxidizing agents, on the other hand, are reduced (gain electrons) and facilitate the oxidation of other atoms (removal of electrons from other atoms). Oxidation of an atom does not depend on the Gibbs free energy; therefore, oxidation can be spontaneous or nonspontaneous.
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In general, the reduction of a ketone to an alcohol can be accomplished by all of the following except one. Which one will not reduce a ketone?
In general, the reduction of a ketone to an alcohol can be accomplished by all of the following except one. Which one will not reduce a ketone?
is the only option that will not reduce a ketone to an alcohol, simply because it is not a reducing agent like the other four—it is an oxidizing agent. The addition of oxygens to a ketone will not yield an alcohol (oxidation). The addition of hydrogen to a ketone will yield an alcohol (reduction). The other answer options are reducing agents that would facilitate this reaction.
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In which of the following reactions is sodium reduced?
In which of the following reactions is sodium reduced?
Reduction involves gain of electrons whereas oxidation involves loss of electrons. In reduction, the oxidation number becomes more negative (due to gain of electrons) whereas in oxidation, the oxidation number becomes more positive. Sodium is an alkali metal, found on the first column of the periodic table. Every atom in this column has one valence electron; therefore, to complete its octet every alkali metal will lose an electron and will have an oxidation number of 
. It is very hard to oxidize and reduce these metals because of its desire to maintain octet; therefore, sodium can never be reduced or oxidized (it will always have an oxidation number of 
).
Reduction involves gain of electrons whereas oxidation involves loss of electrons. In reduction, the oxidation number becomes more negative (due to gain of electrons) whereas in oxidation, the oxidation number becomes more positive. Sodium is an alkali metal, found on the first column of the periodic table. Every atom in this column has one valence electron; therefore, to complete its octet every alkali metal will lose an electron and will have an oxidation number of
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A molecule undergoing oxidation __________ protons and a molecule undergoing reduction __________ protons.
A molecule undergoing oxidation __________ protons and a molecule undergoing reduction __________ protons.
Oxidation and reduction involve loss and gain of electrons, respectively. It does not involve loss or gain of protons. Recall that the identity of an atom is changed when the amount of protons change; therefore, it is very hard to change the amount of protons. Only few reactions (such as nuclear decay reactions) can change the number of protons and alter the identity of an atom.
Oxidation and reduction involve loss and gain of electrons, respectively. It does not involve loss or gain of protons. Recall that the identity of an atom is changed when the amount of protons change; therefore, it is very hard to change the amount of protons. Only few reactions (such as nuclear decay reactions) can change the number of protons and alter the identity of an atom.
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