Question 1

In which one of the following compounds is the oxidation number of S equal to +4?

Accepted Answer

In Na2SO3, the oxidation state of S is +4. This is determined by knowing that the oxidation state of Na is +1 (for each Na, contributing a total of +2) and that of oxygen is -2 (for each O, contributing a total of -6 for three oxygens). The sum of the oxidation states in a neutral compound is zero, so for sulfur in Na2SO3, it must be +4 to balance the -4 from two Na ions and -6 from three oxygen ions, resulting in a total charge of 0.

Question 2

Nitrogen-fixing bacteria and plants are capable of converting atmospheric nitrogen (N₂) to ammonia (NH₃). This process is an example of ________

Accepted Answer

The conversion of atmospheric nitrogen to ammonia involves gaining electrons, therefore it is a reduction reaction. Nitrogen has an oxidation state of 0 in atmospheric nitrogen and an oxidation state of -3 in ammonia, indicating that it has gained three electrons.

Question 3

Magnesium metal burns brightly in the air to make a white powder. What are the likely products?

Accepted Answer

When magnesium burns, it reacts with oxygen in the air to form magnesium oxide (MgO). It may also react with nitrogen in the air to form magnesium nitride (Mg3N2). Therefore, the likely products of magnesium burning are MgO and possibly Mg3N2. Choice D is the only option that includes MgO as one of the products, so it is the best choice.

Question 4

Lead sinkers used for saltwater fishing do not react with sodium ions in the water. From this we can infer that ________

Accepted Answer

The fact that lead sinkers do not react with sodium ions in saltwater implies that the sodium ions cannot oxidize the lead. Therefore, option D is the correct inference. Option E is also correct as the fact that the lead sinkers do not react with sodium ions suggests that sodium ions cannot reduce lead. Options A, B, and C are incorrect as they imply that lead can react with sodium ions in some way, which is not supported by the given information.

Question 5

Tube worms that survive near geothermal vents of hydrogen sulfide rely on bacteria living inside them to obtain energy by the oxidation of H₂S to SO₄^2-. What is the overall change in the oxidation number of sulfur for this reaction?

Accepted Answer

In the reaction, sulfur is oxidized from an oxidation state of -2 in hydrogen sulfide (HS^−) to an oxidation state of +6 in sulfate (SO_4^2−). The overall change in the oxidation number of sulfur is therefore +8.

Question 6

The carbon cycle characterizes the cyclic transformations of the element carbon through the environment and biomass. Some of the important species in this cycle are CO₂, CO₃^2-, C₆H₁₂O₆, and CH₄. Which of these compounds would undergo complete oxidation by O₂ to give the largest change in oxidation number?

Accepted Answer

The compound CH₄ has a carbon atom with an oxidation state of -4 (each hydrogen has an oxidation state of +1, and the sum of the oxidation states must be equal to the charge on the molecule, which is 0). Complete oxidation of the carbon in CH₄ would involve adding 4 electrons to it, resulting in an oxidation state of +4. This is the largest change in oxidation number among the given compounds.

Question 7

In the following reaction, which element or ion is reduced? Cl₂(g) NaBr(aq) NaCl(aq) Br₂(g)

Accepted Answer

In the given reaction, Cl has a higher oxidation state (+1) in the reactant Cl₂ and a lower oxidation state (-1) in the product NaCl(aq). Therefore, Cl is undergoing reduction and the correct answer is C.

Question 8

When the oxidation reduction reaction shown here is balanced, how many electrons are transferred for each atom of copper that reacts? Ag⁺(aq) Cu(s) Ag(s) Cu²⁺(aq)

Accepted Answer

In the balanced equation, each copper atom loses two electrons and each silver ion gains one electron. Therefore, two electrons are transferred for each atom of copper that reacts.

Question 9

In the following reaction, which element is oxidized? Cu FeSO₄ Fe CuSO₄

Accepted Answer

The answer of In the following reaction, which element is...

Question 10

In which one of the following compounds is the oxidation number of silicon not equal to +4?

Accepted Answer

The answer of In which one of the following compounds...

Question 11

Dinitrogen monoxide (N₂O) is produced from nitrate ions in aqueous solution by anaerobic bacteria. Which one of the following statements about this reaction is not correct? 2NO₃^-(aq) H₂O(l ) N₂O(g) 2O₂(g) 2OH^-(aq)

Accepted Answer

The statement that is not correct is E. As written above, four electrons are transferred from nitrogen to oxygen, not from oxygen to nitrogen, in this reaction. Therefore, statement E should be corrected as follows: As written above, four electrons are transferred from nitrate to nitrogen in this reaction. The other statements are correct. Nitrate is the oxidizing agent because it causes nitrogen to be reduced and oxygen to be oxidized. Oxygen is oxidized because it loses electrons and nitrogen is reduced because it gains electrons. Water can be written as a reactant in the oxidation half reaction because it is formed when oxygen gains electrons.

Question 12

In which one of the following compounds is the oxidation number of phosphorus equal to +5?

Accepted Answer

The answer of In which one of the following compounds...

Question 13

In which compound does chlorine have an oxidation number of +5?

Accepted Answer

The answer of In which compound does chlorine have an...

Question 14

Groundwater often has low levels of dissolved oxygen because it is not continually exposed to the atmosphere. When groundwater reaches the surface, the following reaction involving soluble iron(II) can occur. What are the oxidation numbers of the elements in the product, Fe(OH)₃? 4Fe²⁺(aq) O₂(g) 2H₂O(l ) 8OH^- 4Fe(OH)₃(s)

Accepted Answer

The answer of Groundwater often has low levels of dissolved...

Question 15

The half-reaction for the reduction of molecular oxygen to water is ________

Accepted Answer

The correct half-reaction for the reduction of molecular oxygen to water is:
O2 (g) + 4H+ + 4e- → 2H2O (l)
None of the given options match this reaction exactly, but the closest option is D, which combines two half-reactions:
2H+ + 2e- → H2 (g) (incorrect half-reaction)
O2 (g) + 4H+ + 4e- → 2H2O (l) (correct half-reaction)
The incorrect half-reaction in D should be disregarded as it does not relate to the reduction of oxygen to water.

Question 16

In a spontaneous oxidation reduction reaction between aluminum and silver ion, the aluminum(III) ion and solid silver are formed. If 0.1 mol of aluminum is consumed in this reaction, how much silver will be produced?

Accepted Answer

In the reaction, 2 Al + 3 Ag⁺ → 2 Al³⁺ + 3 Ag, 2 moles of Al produce 3 moles of Ag. Therefore, 0.1 mol of Al will produce 0.15 mol of Ag, which is closest to 0.3 mol when considering stoichiometry and rounding.

Question 17

Based on the activity series shown below, which of the following statements is true?

Accepted Answer

The answer of Based on the activity series shown below,...

Question 18

In going from the top to the bottom of the activity series below, the ease of oxidation of the metal ________, which means that ________.

Accepted Answer

In going from the top to the bottom of the activity series, the ease of oxidation of the metal decreases, which means that a metal higher in the activity series can reduce the ions of a metal lower in the activity series. Therefore, magnesium, which is higher in the activity series, can reduce zinc ions.

Question 19

What is the oxidation number of P in H₂PO₄^-?

Accepted Answer

The oxidation number of P in HPO4^2- is +5. This is determined by considering the oxidation states of the other elements and the overall charge of the ion. H has an oxidation state of +1, O typically has an oxidation state of -2, and the overall charge is -2. To balance the charges, P must have an oxidation state of +5.

Question 20

The concentration of iron(II) ions in water can be determined by titration with potassium permanganate in acid solution as shown by the incomplete unbalanced reaction equation below. Identify the stoichiometric coefficient of the iron(II) ion in the balanced reaction equation. Fe²⁺(aq) MnO₄^- Fe³⁺(aq) Mn²⁺(aq)

Accepted Answer

The answer of The concentration of iron(II) ions in water...

Quiz 4: Solution Chemistry: The Hydrosphere

In which one of the following compounds is the oxidation number of S equal to +4?

Nitrogen-fixing bacteria and plants are capable of converting atmospheric nitrogen (N₂) to ammonia (NH₃) . This process is an example of ________

Magnesium metal burns brightly in the air to make a white powder. What are the likely products?

Lead sinkers used for saltwater fishing do not react with sodium ions in the water. From this we can infer that ________

Tube worms that survive near geothermal vents of hydrogen sulfide rely on bacteria living inside them to obtain energy by the oxidation of H₂S to SO₄^2-. What is the overall change in the oxidation number of sulfur for this reaction?

In the following reaction, which element or ion is reduced? Cl₂(g) NaBr(aq) NaCl(aq) Br₂(g)

When the oxidation reduction reaction shown here is balanced, how many electrons are transferred for each atom of copper that reacts? Ag⁺(aq) Cu(s) Ag(s) Cu²⁺(aq)

In the following reaction, which element is oxidized? Cu FeSO₄ Fe CuSO₄

In which one of the following compounds is the oxidation number of silicon not equal to +4?

Dinitrogen monoxide (N₂O) is produced from nitrate ions in aqueous solution by anaerobic bacteria. Which one of the following statements about this reaction is not correct? 2NO₃^-(aq) H₂O(l ) N₂O(g) 2O₂(g) 2OH^-(aq)

In which one of the following compounds is the oxidation number of phosphorus equal to +5?

In which compound does chlorine have an oxidation number of +5?

The half-reaction for the reduction of molecular oxygen to water is ________

In a spontaneous oxidation reduction reaction between aluminum and silver ion, the aluminum(III) ion and solid silver are formed. If 0.1 mol of aluminum is consumed in this reaction, how much silver will be produced?

Based on the activity series shown below, which of the following statements is true?

In going from the top to the bottom of the activity series below, the ease of oxidation of the metal , which means that .

What is the oxidation number of P in H₂PO₄^-?

Quiz 4: Solution Chemistry: The Hydrosphere

In which one of the following compounds is the oxidation number of S equal to +4?

Nitrogen-fixing bacteria and plants are capable of converting atmospheric nitrogen (N2) to ammonia (NH3) . This process is an example of ________

Magnesium metal burns brightly in the air to make a white powder. What are the likely products?

Lead sinkers used for saltwater fishing do not react with sodium ions in the water. From this we can infer that ________

Tube worms that survive near geothermal vents of hydrogen sulfide rely on bacteria living inside them to obtain energy by the oxidation of H2S to SO42-. What is the overall change in the oxidation number of sulfur for this reaction?

In the following reaction, which element or ion is reduced? Cl2(g) NaBr(aq) NaCl(aq) Br2(g)

When the oxidation reduction reaction shown here is balanced, how many electrons are transferred for each atom of copper that reacts? Ag+(aq) Cu(s) Ag(s) Cu2+(aq)

In the following reaction, which element is oxidized? Cu FeSO4 Fe CuSO4

In which one of the following compounds is the oxidation number of silicon not equal to +4?

Dinitrogen monoxide (N2O) is produced from nitrate ions in aqueous solution by anaerobic bacteria. Which one of the following statements about this reaction is not correct? 2NO3-(aq) H2O(l ) N2O(g) 2O2(g) 2OH-(aq)

In which one of the following compounds is the oxidation number of phosphorus equal to +5?

In which compound does chlorine have an oxidation number of +5?

The half-reaction for the reduction of molecular oxygen to water is ________

In a spontaneous oxidation reduction reaction between aluminum and silver ion, the aluminum(III) ion and solid silver are formed. If 0.1 mol of aluminum is consumed in this reaction, how much silver will be produced?

Based on the activity series shown below, which of the following statements is true?

In going from the top to the bottom of the activity series below, the ease of oxidation of the metal ________, which means that ________.

What is the oxidation number of P in H2PO4-?

Nitrogen-fixing bacteria and plants are capable of converting atmospheric nitrogen (N₂) to ammonia (NH₃) . This process is an example of ________

Tube worms that survive near geothermal vents of hydrogen sulfide rely on bacteria living inside them to obtain energy by the oxidation of H₂S to SO₄^2-. What is the overall change in the oxidation number of sulfur for this reaction?

In the following reaction, which element or ion is reduced? Cl₂(g) NaBr(aq) NaCl(aq) Br₂(g)

When the oxidation reduction reaction shown here is balanced, how many electrons are transferred for each atom of copper that reacts? Ag⁺(aq) Cu(s) Ag(s) Cu²⁺(aq)

In the following reaction, which element is oxidized? Cu FeSO₄ Fe CuSO₄

Dinitrogen monoxide (N₂O) is produced from nitrate ions in aqueous solution by anaerobic bacteria. Which one of the following statements about this reaction is not correct? 2NO₃^-(aq) H₂O(l ) N₂O(g) 2O₂(g) 2OH^-(aq)

In going from the top to the bottom of the activity series below, the ease of oxidation of the metal , which means that .

What is the oxidation number of P in H₂PO₄^-?