Question 1

Which of the following best describes a redox reaction?

Accepted Answer

A reaction that involves the transfer of electrons between reactants.

Question 2

In acidic redox reactions, which species is commonly added to balance oxygen atoms?

Accepted Answer

H$$_2O$$

Question 3

When balancing redox reactions in acidic solution, what is the correct order of steps?

Accepted Answer

Balance all atoms except H and O, then balance O using H$$_2O$$, then balance H using H$$^+$$, then balance charge with electrons.

Question 4

Given the half-reaction: $$MnO_4^- (aq$$) \rightarrow $$Mn^{2+} (aq$$)$$, what is the number of electrons that must be added to balance the charge?

Accepted Answer

$$5$$ electrons

Question 5

In the reaction $$NO_2^- (aq) + Cr_2O$$_$$7^{2-} (aq$$) \rightarrow $$Cr^{3+} (aq$$) + $$NO_3^- (aq$$)$$, which element is reduced?

Accepted Answer

Chromium

Question 6

What is the purpose of adding electrons when balancing half-reactions?

Accepted Answer

To balance the overall charge of each half-reaction.

Question 7

In the reaction $$Cl_2 (g) + S_2O$$_$$3^{2-} (aq$$) \rightarrow Cl^- (aq) + $$SO_4$$^{2-} (aq)$$, which species acts as the oxidizing agent?

Accepted Answer

$$Cl_2$$

Question 8

When balancing the following redox reaction in acidic solution, what is the coefficient of $$Fe^{2+}$$?
$$Bi^{3+} (aq$$) + $$Fe^{3+} (aq) + H_2O (l$$) \rightarrow $$BiO_3^- (aq$$) + $$Fe^{2+} (aq) + H^+ (aq$$)$$

Accepted Answer

$$6$$

Question 9

Which of the following is TRUE about half-reactions in redox processes?

Accepted Answer

Each half-reaction represents either oxidation or reduction and must be balanced for both mass and charge.

Question 10

In the half-reaction $$Cr_2O_7$$^{2-}$$ (aq) \rightarrow Cr$$^{3+}$$ (aq)$$, how many water molecules are needed to balance the oxygen atoms?

Accepted Answer

$$7 H$_2O$

Question 11

Which statement best explains why redox reactions are important in biological systems?

Accepted Answer

They are responsible for energy production through electron transfer, such as in cellular respiration.

Question 12

In balancing redox reactions, why is it necessary to multiply the half-reactions by appropriate factors before adding them together?

Accepted Answer

To ensure the number of electrons lost equals the number gained.

Question 13

Which of the following is the correct balanced half-reaction for the reduction of $$MnO_4$$^-$$ to Mn$$^{2+}$$ in acidic solution?

Accepted Answer

$$MnO_4^- + 8H^+ + 5e$$^- \rightarrow $$Mn^{2+} + 4H_2O$

Question 14

A student is balancing the following redox reaction in acidic solution: $$Cl_2 (g) + S_2O$$_$$3^{2-} (aq$$) \rightarrow Cl^- (aq) + $$SO_4$$^{2-} (aq)$$. Which step should they perform after balancing all atoms except H and O?

Accepted Answer

Balance oxygen atoms by adding H$$_2O.$$

Question 15

In the half-reaction $$NO_2$$^- \rightarrow $$NO_3$$^-$$, what is the change in oxidation state of nitrogen?

Accepted Answer

It increases from +3 to +5.

Question 16

Which of the following is a correct reason for using H$$^+$$ ions when balancing redox reactions in acidic solution?

Accepted Answer

To balance the number of hydrogen atoms.

Question 17

A medical laboratory is analyzing a patient's blood for iron content. Which redox reaction is most relevant for determining the amount of Fe$$^{2+}$$ present?

Accepted Answer

$$Fe^{2+}$$ \rightarrow $$Fe^{3+} + e$$^-$$

Question 18

Which of the following is NOT a correct step in balancing redox reactions in acidic solution?

Accepted Answer

Balance oxygen atoms by adding OH$$^-.$$

Question 19

In the reaction $$Bi^{3+} (aq$$) + $$Fe^{3+} (aq) + H_2O (l$$) \rightarrow $$BiO_3^- (aq$$) + $$Fe^{2+} (aq) + H^+ (aq$$)$$, which species is oxidized?

Accepted Answer

$$Bi^{3+} to$$ $$BiO_3$$^-$$

Balancing Redox Reactions in Acidic Solutions: Study Notes

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