General Chemistry - MCAT Chemical and Physical Foundations of Biological Systems
Card 1 of 3171
Fundamental, or f orbitals, have shapes that are quite complex and difficult to draw. How many suborbitals are there in the f block?
Fundamental, or f orbitals, have shapes that are quite complex and difficult to draw. How many suborbitals are there in the f block?
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The f orbital is expressed in the lanthanides and the actinides. These groups contain fourteen elements in each row. Since each suborbital can contain two electrons, the correct answer is fourteen divided by two, or seven.
The trend for suborbitals is determined by the l quantum number. The number of possible values for l determine the number of subshells.
The f orbital is expressed in the lanthanides and the actinides. These groups contain fourteen elements in each row. Since each suborbital can contain two electrons, the correct answer is fourteen divided by two, or seven.
The trend for suborbitals is determined by the l quantum number. The number of possible values for l determine the number of subshells.
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How many electrons can fit in the 
electron shell?
How many electrons can fit in the
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An 
shell contains 3s, 3d, and 3p subshells. Any s shell can hold up to two electrons, any p shell can hold six electrons, and any d shell can hold ten electrons.
This question is best solved by using quantum numbers. We are given the principle quantum number. Using this, we can work down to determine how many electrons can fit in this shell. The rules for quantum numbers are given below.
If the principle quantum number is three, then the next quantum number can be zero, one, or two. These correspond to the s, p, and d subshells, respectively.
After that, the next quantum number describes the orbitals within the subshells. Each orbital can carry two electrons, according to the final quantum number.
In total, there are eighteen electrons allowed in all subshells of the third energy level.
An
This question is best solved by using quantum numbers. We are given the principle quantum number. Using this, we can work down to determine how many electrons can fit in this shell. The rules for quantum numbers are given below.
If the principle quantum number is three, then the next quantum number can be zero, one, or two. These correspond to the s, p, and d subshells, respectively.
After that, the next quantum number describes the orbitals within the subshells. Each orbital can carry two electrons, according to the final quantum number.
In total, there are eighteen electrons allowed in all subshells of the third energy level.
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What is the molarity of a 1L solution composed of water and 300g of sodium iodide?
What is the molarity of a 1L solution composed of water and 300g of sodium iodide?
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Sodium iodide is given by the formula NaI, and has a molecular weight of 150g/mol. Molarity is found by dividing the moles of solute by liters of solvent.
We find the moles of sodium iodide by using the mass (300g) and molecular weight.
We know our volume is 1L, so now we can solve for the molarity.
Sodium iodide is given by the formula NaI, and has a molecular weight of 150g/mol. Molarity is found by dividing the moles of solute by liters of solvent.
We find the moles of sodium iodide by using the mass (300g) and molecular weight.
We know our volume is 1L, so now we can solve for the molarity.
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All of the following are true regarding a solution except .
All of the following are true regarding a solution except .
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Solutions can occur in all three phases of matter. They can also occur between two compounds in a single phase. For example, brass is a solution of two metals: zinc and copper.
Solutions can occur in all three phases of matter. They can also occur between two compounds in a single phase. For example, brass is a solution of two metals: zinc and copper.
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Which of the following types of radioactive decay alters the mass number?
Which of the following types of radioactive decay alters the mass number?
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The mass number is the total number of nucleons (protons and neutrons) in an atom's nucleus. An atom that undergoes alpha decay will lose a helium nucleus. This decreases its mass number by four. All other forms of radioactive decay listed alter the atomic number of the atom, but not the mass number.
Beta emission involves the conversion of a neutron to a proton and an electron, but only expels the electron.
Electron capture involves the conversion of a proton and an electron into a neutron.
Positron emission involves the conversion of a proton to a neutron and a "positron," or positively charged electron.
The mass number is the total number of nucleons (protons and neutrons) in an atom's nucleus. An atom that undergoes alpha decay will lose a helium nucleus. This decreases its mass number by four. All other forms of radioactive decay listed alter the atomic number of the atom, but not the mass number.
Beta emission involves the conversion of a neutron to a proton and an electron, but only expels the electron.
Electron capture involves the conversion of a proton and an electron into a neutron.
Positron emission involves the conversion of a proton to a neutron and a "positron," or positively charged electron.
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What is the electron configuration of chlorine?
What is the electron configuration of chlorine?
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Each period (row) of the periodic table corresponds to a principle quantum number, or electron energy shell. An electron is added for each element as one moves across the period. The first two electrons (groups 1 and 2) are placed in the s subshell. The next six electrons (groups 13 through 18) are placed in the p subshell.
Chlorine has an atomic number of 17, meaning that it will have a total of 17 electrons distributed through these shells and subshells. Start at the 1s subshell and work upward. Note that there is no 1p subshell.
Chlorine: 1s22s22p63s23p5
Another way of writing electron configuration for an element is to first write the noble gas that comes immediately before that element in brackets, and then write the rest of the notation. For example, the bracket notation for chlorine would be: \[Ne\]3s23p5.
Each period (row) of the periodic table corresponds to a principle quantum number, or electron energy shell. An electron is added for each element as one moves across the period. The first two electrons (groups 1 and 2) are placed in the s subshell. The next six electrons (groups 13 through 18) are placed in the p subshell.
Chlorine has an atomic number of 17, meaning that it will have a total of 17 electrons distributed through these shells and subshells. Start at the 1s subshell and work upward. Note that there is no 1p subshell.
Chlorine: 1s22s22p63s23p5
Another way of writing electron configuration for an element is to first write the noble gas that comes immediately before that element in brackets, and then write the rest of the notation. For example, the bracket notation for chlorine would be: \[Ne\]3s23p5.
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Le Chatlier's principle states that when a stressor is introduced to a system, the system will shift its equilibrium state as a way of countering the stress. What are the factors (stressors) that apply to Le Chatlier's principle?
Le Chatlier's principle states that when a stressor is introduced to a system, the system will shift its equilibrium state as a way of countering the stress. What are the factors (stressors) that apply to Le Chatlier's principle?
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Le Chatelier's principle emphasizes three main stressors: changes in temperature, pressure, and concentration of reactants and products. If any of these three stressors are added, the Keq will shift in a way that counters this added stress. Temperature and concentration changes will affect any reaction, while pressure changes will only have a marked effect on reactions involving at least one gaseous compound.
Le Chatelier's principle emphasizes three main stressors: changes in temperature, pressure, and concentration of reactants and products. If any of these three stressors are added, the Keq will shift in a way that counters this added stress. Temperature and concentration changes will affect any reaction, while pressure changes will only have a marked effect on reactions involving at least one gaseous compound.
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Which molecule has the shortest bond between two carbons?
Which molecule has the shortest bond between two carbons?
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Bond distance is related to the type of bond between the two atoms. The more bonds between two atoms, the shorter the distance. In other words, a triple bond is shorter than a double bond, and a double bond is shorter than a single bond. Ethyne is the only option that has a triple bond between the carbons, so it has the shortest bond distance.
Bond distance is related to the type of bond between the two atoms. The more bonds between two atoms, the shorter the distance. In other words, a triple bond is shorter than a double bond, and a double bond is shorter than a single bond. Ethyne is the only option that has a triple bond between the carbons, so it has the shortest bond distance.
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Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
A scientist undertakes an effort to visualize the electron cloud that makes up the single O-H bond. You tell him that this will be complicated by the fact that the more you know about an electron's momentum, the less you know about its position, and vice versa. What principle are you describing?
Electronegativity is an important concept in physical chemistry, and often used to help quantify the dipole moment of polar compounds. Polar compounds are different from those compounds that are purely nonpolar or purely ionic. An example can be seen by contrasting sodium chloride, NaCl, with an organic molecule, R-C-OH. The former is purely ionic, and the latter is polar covalent.
When comparing more than one polar covalent molecule, we use the dipole moment value to help us determine relative strength of polarity. Dipole moment, however, is dependent on the electronegativity of the atoms making up the bond. Electronegativity is a property inherent to the atom in question, whereas dipole moment is a property of the bond between them.
For example, oxygen has an electronegativity of 3.44, and hydrogen of 2.20. In other words, oxygen more strongly attracts electrons when in a bond with hydrogen. This leads to the O-H bond having a dipole moment.
When all the dipole moments of polar bonds in a molecule are summed, the molecular dipole moment results, as per the following equation.
Dipole moment = charge * separation distance
A scientist undertakes an effort to visualize the electron cloud that makes up the single O-H bond. You tell him that this will be complicated by the fact that the more you know about an electron's momentum, the less you know about its position, and vice versa. What principle are you describing?
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The Heisenberg Uncertainty Principle tells us exactly this. At the quantum level, the more you know about a body's momentum, the less you know about its position.
The Heisenberg Uncertainty Principle tells us exactly this. At the quantum level, the more you know about a body's momentum, the less you know about its position.
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Photons can be generated with different wavelengths, depending on the number of energy levels available. What is the minimum number of different energy levels needed to produce six different wavelengths of light?
Photons can be generated with different wavelengths, depending on the number of energy levels available. What is the minimum number of different energy levels needed to produce six different wavelengths of light?
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From Bohr's model of the hydrogen atom, we know that as electrons jump to a higher energy state they become more excited, and absorb more energy. Additionally, we know that when an electron moves from a higher energy state to a lower energy state, it releases energy in the form of a photon. Because the emitted photon can be characterized by its wavelength, each jump between two different energy states will have a unique and different wavelength.
To produce six different wavelengths, we would need four different energy levels: n=1, n=2, n=3, n=4. The different wavelengths produced could be described by the following energy transitions.
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4 
1
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4 
2
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4 
3
-
3 
2
-
3 
1
-
2 
1
From Bohr's model of the hydrogen atom, we know that as electrons jump to a higher energy state they become more excited, and absorb more energy. Additionally, we know that when an electron moves from a higher energy state to a lower energy state, it releases energy in the form of a photon. Because the emitted photon can be characterized by its wavelength, each jump between two different energy states will have a unique and different wavelength.
To produce six different wavelengths, we would need four different energy levels: n=1, n=2, n=3, n=4. The different wavelengths produced could be described by the following energy transitions.
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4
-
4
-
4
-
3
-
3
-
2
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Suppose an electron is excited from its ground state to 
. Which of the following effects is most likely to occur?
Suppose an electron is excited from its ground state to
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This question is testing your knowledge of what happens when an electron is excited. Electron excitation always accompanies an increase in energy, the opposite of which is equally true for electrons that fall back toward the ground state. Electron energy transitions are accompanied by electromagnetic energy consumption or release. When an electron increases in energy, it absorbs a certain unit of electromagnetic energy: a photon. When the electron decreases in energy, it emits the lost energy by releasing a photon.
This question is testing your knowledge of what happens when an electron is excited. Electron excitation always accompanies an increase in energy, the opposite of which is equally true for electrons that fall back toward the ground state. Electron energy transitions are accompanied by electromagnetic energy consumption or release. When an electron increases in energy, it absorbs a certain unit of electromagnetic energy: a photon. When the electron decreases in energy, it emits the lost energy by releasing a photon.
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Light waves are known to exist in a wave-particle duality. When objects approach the speed of light, this duality supposedly extends to other forms of matter. A 
lead pencil point weighs roughly 
. If all of this mass was converted into wave energy, how much energy would be released?
Light waves are known to exist in a wave-particle duality. When objects approach the speed of light, this duality supposedly extends to other forms of matter. A
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This is a problem utilizing Einstein's equation:
Before we can solve for the energy, we need to convert the mass to kilograms.
Use this mass and the speed of light to solve for the energy.
This is a problem utilizing Einstein's equation:
Before we can solve for the energy, we need to convert the mass to kilograms.
Use this mass and the speed of light to solve for the energy.
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Which of the following statements are true when there are two electrons in the 
subshell?
Which of the following statements are true when there are two electrons in the
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Electrons occupying the same exact subshell are essentially equivalent. The only thing that differs between them is spin. Because of the Pauli exclusion principle, the electrons musthave opposite spins when occupying the same subshell in an atom. There is nothing to suggest any electrons are being absorbed or emitted.
Electrons occupying the same exact subshell are essentially equivalent. The only thing that differs between them is spin. Because of the Pauli exclusion principle, the electrons musthave opposite spins when occupying the same subshell in an atom. There is nothing to suggest any electrons are being absorbed or emitted.
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Which of the following is the oxidizing agent in the following equation?
Which of the following is the oxidizing agent in the following equation?
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An oxidizing agent is one that oxidizes another element and, becomes reduced in the process. Oxidizing and reducing agents are found in the reactants of the equation, eliminating Al3+ and Cr(s) as answer choices. Cr3+ gains three electrons to become Cr(s), which has an oxidation number of zero. Cr3+ becomes reduced, while Al(s) is oxidized, therefore, Cr3+ is the oxidizing agent. Remember "OIL RIG": Oxidation Is Loss of electrons and Reduction Is Gain of electrons.
An oxidizing agent is one that oxidizes another element and, becomes reduced in the process. Oxidizing and reducing agents are found in the reactants of the equation, eliminating Al3+ and Cr(s) as answer choices. Cr3+ gains three electrons to become Cr(s), which has an oxidation number of zero. Cr3+ becomes reduced, while Al(s) is oxidized, therefore, Cr3+ is the oxidizing agent. Remember "OIL RIG": Oxidation Is Loss of electrons and Reduction Is Gain of electrons.
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In the above unbalanced redox reaction, which best describes the oxidation/reduction roles of iron and oxygen?
In the above unbalanced redox reaction, which best describes the oxidation/reduction roles of iron and oxygen?
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There are a couple options to solve this problem. First, we could simply remember that anything which combines with oxygen in a redox reaction is oxidized, and the associated oxygen is reduced.
Another option is to think about the oxidation numbers of each element (an element whose oxidation number increases is oxidized, and one whose oxidation number decreases is reduced). If we choose this method, recall that free elements (Fe and O2 in this case) have oxidation number 0. Also, oxygen in compounds has oxidation number -2. Oxygen's oxidation number decreases from 0 to -2, meaning that oxygen is reduced. Since oxidation and reduction occur at the same time in different elements of the redox reaction, iron's oxidation number must increase, so iron is oxidized.
There are a couple options to solve this problem. First, we could simply remember that anything which combines with oxygen in a redox reaction is oxidized, and the associated oxygen is reduced.
Another option is to think about the oxidation numbers of each element (an element whose oxidation number increases is oxidized, and one whose oxidation number decreases is reduced). If we choose this method, recall that free elements (Fe and O2 in this case) have oxidation number 0. Also, oxygen in compounds has oxidation number -2. Oxygen's oxidation number decreases from 0 to -2, meaning that oxygen is reduced. Since oxidation and reduction occur at the same time in different elements of the redox reaction, iron's oxidation number must increase, so iron is oxidized.
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Consider the following combustion reaction.
Which of the following statements correctly describes carbon in the reaction?
Consider the following combustion reaction.
Which of the following statements correctly describes carbon in the reaction?
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This problem requires us to determine the oxidation number of carbon as a reactant and as a product. The oxidation number of carbon as a reactant is –4, because it is attached to four hydrogens each with a charge of +1. The overall charge on the molecule is zero, the carbon must cancel out the charges contributed by hydrogen.
Carbon as a product has an oxidation number of +4, because it is attached to two oxygens, each with an oxidation number of –2. Again, we know that the molecule is neutral, and carbon must balance the charges from oxygen
Since the oxidation number of carbon went from –4 to +4, we conclude that carbon has been oxidized in the reaction. Any atom that loses electrons is oxidized, while any atom to gain electrons is reduced.
This problem requires us to determine the oxidation number of carbon as a reactant and as a product. The oxidation number of carbon as a reactant is –4, because it is attached to four hydrogens each with a charge of +1. The overall charge on the molecule is zero, the carbon must cancel out the charges contributed by hydrogen.
Carbon as a product has an oxidation number of +4, because it is attached to two oxygens, each with an oxidation number of –2. Again, we know that the molecule is neutral, and carbon must balance the charges from oxygen
Since the oxidation number of carbon went from –4 to +4, we conclude that carbon has been oxidized in the reaction. Any atom that loses electrons is oxidized, while any atom to gain electrons is reduced.
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Consider the following reaction.
Which of the following atoms is oxidized in the reaction?
Consider the following reaction.
Which of the following atoms is oxidized in the reaction?
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The atom that is oxidized will have a higher oxidation number as a reactant than as a product. Since reactant phosphorus (P4) is in elemental form, it has an oxidation number of 0. As a product, phosphorus (PO43-) has an oxidation number of +5.
Total charge = (P) + 4(O) = –3
–3 = (P) + 4(–2) = (P) + (–8)
p = +5
Because it is now more positive, we say that the phosphorus has been oxidized.
The atom that is oxidized will have a higher oxidation number as a reactant than as a product. Since reactant phosphorus (P4) is in elemental form, it has an oxidation number of 0. As a product, phosphorus (PO43-) has an oxidation number of +5.
Total charge = (P) + 4(O) = –3
–3 = (P) + 4(–2) = (P) + (–8)
p = +5
Because it is now more positive, we say that the phosphorus has been oxidized.
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Consider the following reaction.
What is the oxidizing reagent in the reaction?
Consider the following reaction.
What is the oxidizing reagent in the reaction?
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The oxidizing reagent is the reactant, not the atom, that is responsible for receiving electrons from another atom in order to oxidize it. The oxygen gas goes from having an oxidation number of 0 to –2. This means that oxygen gas is reduced, but because it oxidized another atom by taking its electrons, we call it the oxidizing reagent.
Reactant oxygen is elemental, and has oxidation number 0.
Product oxygen is in H2O, with net charge of 0.
Total charge = 2(H) + (O) = 0
2(+1) + (O) = 2 + (O) = 0
O = –2
Decrease in oxidation number indicates reduction, and also identifies the oxidizing agent.
The oxidizing reagent is the reactant, not the atom, that is responsible for receiving electrons from another atom in order to oxidize it. The oxygen gas goes from having an oxidation number of 0 to –2. This means that oxygen gas is reduced, but because it oxidized another atom by taking its electrons, we call it the oxidizing reagent.
Reactant oxygen is elemental, and has oxidation number 0.
Product oxygen is in H2O, with net charge of 0.
Total charge = 2(H) + (O) = 0
2(+1) + (O) = 2 + (O) = 0
O = –2
Decrease in oxidation number indicates reduction, and also identifies the oxidizing agent.
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Consider the following oxidation-reduction reaction.
Which of the following statements is true?
Consider the following oxidation-reduction reaction.
Which of the following statements is true?
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In the reaction, solid potassium (K) is initially in elemental form, so it has an oxidation state of 0. The potassium ions (K+) have a charge of +1 in the product. Since the potassium has lost an electron, it has been oxidized.
Since each hydrogen in reactants (NH3) has an oxidation state of +1, and the hydrogen gas (H2) has a charge of 0 as a product, the hydrogen has been reduced. Since it was reduced, we conclude that NH3 is the oxidizing reagent for the reaction.
In the reaction, solid potassium (K) is initially in elemental form, so it has an oxidation state of 0. The potassium ions (K+) have a charge of +1 in the product. Since the potassium has lost an electron, it has been oxidized.
Since each hydrogen in reactants (NH3) has an oxidation state of +1, and the hydrogen gas (H2) has a charge of 0 as a product, the hydrogen has been reduced. Since it was reduced, we conclude that NH3 is the oxidizing reagent for the reaction.
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Which compound is oxidized in the following reaction?
Which compound is oxidized in the following reaction?
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Oxidation is defined by a loss of electrons, generally resulting in a more positive charge on an atom. Reduction is defined by a gain of electrons, generally resulting in a more negative charge on an atom. To identify the compound being oxidized, we need to find which compound is becoming more positive.
Zinc is initially neutral, but gains a positive two charge as a product. Hydrogen initially has one positive charge, but becomes neutral in the product. The distinction becomes even clearer if we break the overall reaction into two half-reactions.
We can see that zinc is losing electrons and hydrogen is gaining electrons. Zinc is thus being oxidized.
Oxidation is defined by a loss of electrons, generally resulting in a more positive charge on an atom. Reduction is defined by a gain of electrons, generally resulting in a more negative charge on an atom. To identify the compound being oxidized, we need to find which compound is becoming more positive.
Zinc is initially neutral, but gains a positive two charge as a product. Hydrogen initially has one positive charge, but becomes neutral in the product. The distinction becomes even clearer if we break the overall reaction into two half-reactions.
We can see that zinc is losing electrons and hydrogen is gaining electrons. Zinc is thus being oxidized.
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