Electrochemistry Test 3

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MCQs 1:

What is the oxidation number of oxygen in the compound OF2?





Topic: Oxidation Numbers in Chemical Compounds

Correct Answer: C) +2

Detailed Hint:
  • Oxidation numbers are assigned to atoms in a molecule to help in understanding the oxidation and reduction happening in a reaction.
  • Typically, in most compounds, oxygen has an oxidation state of -2. However, there are exceptions when oxygen is bonded with certain highly electronegative elements.
  • In the case of OF2, Oxygen is bonded with Fluorine, which is more electronegative than oxygen. This results in the assignment of an oxidation number of -1 for Fluorine and correspondingly, a positive oxidation number for Oxygen.
  • Hence, in OF2, Oxygen ends up with an oxidation state of +2. Therefore, the correct answer is C) +2.

MCQs 2:

What kind of charge does a cathode possess in an electrolytic cell?





Topic: Charges in Electrolytic Cells

Correct Answer: B) Negative

Detailed Hint:
  • In an electrolytic cell, the process of electrolysis occurs, which is essentially the breaking down of complex molecules into simpler ones using electric current.
  • During this process, oxidation happens at the anode and reduction at the cathode.
  • Although the processes at the anode and cathode are consistent with other cells, their charges are opposite. In an electrolytic cell, the anode is positively charged, and the cathode is negatively charged.
  • Therefore, the correct answer is B) Negative.

MCQs 3:

Which cell carries out a non-spontaneous redox reaction by passing an electric current?





Topic: Types of Electrochemical Cells

Correct Answer: D) Electrolytic cell

Detailed Hint:
  • A non-spontaneous redox reaction is one that needs an external energy supply, like an electric current, to take place.
  • While Galvanic, Voltaic, and Daniell cells are all types of cells that allow spontaneous redox reactions to happen, only the Electrolytic cell is designed to facilitate non-spontaneous reactions.
  • An electrolytic cell uses an external source of voltage to bring about a chemical change.
  • Hence, the correct answer is D) Electrolytic cell.

MCQs 4:

What is the term used for the apparent charge on an atom in a molecule?





Topic: Chemical Bonds and Charges

Correct Answer: C) Oxidation number

Detailed Hint:
  • The apparent charge on an atom in a molecule is a concept used in the study of chemical bonding and reactions.
  • This concept is not about the valency (which is the combining power of an atom), nor the coordination number (which is the total number of neighbors an atom has), or the charge number (which is a misnomer).
  • The correct term for this concept is the "oxidation number". It is used to understand the distribution of electrons among atoms in a molecule and plays a fundamental role in the study of redox reactions.
  • Therefore, the correct answer is C) Oxidation number.

MCQs 5:

What is the oxidation number of nitrogen in NO3-1?





Topic: Oxidation Numbers in Nitrate Ion

Correct Answer: D) +5

Detailed Hint:
  • Oxidation states are crucial in determining and understanding the chemical composition and structure of molecules.
  • In the case of NO3-1, or nitrate ion, nitrogen is bonded to oxygen, which typically has an oxidation state of -2.
  • To find the oxidation state of nitrogen, we can set up the equation x + (-2*3) = -1, where x is the oxidation state of Nitrogen.
  • When we solve for x, we get x = +5. Therefore, the correct answer is D) +5.

MCQs 6:

What is considered as the potential of the Standard Hydrogen Electrode (SHE)?





Topic: Electrochemical Potential

Correct Answer: A) Zero

Detailed Hint:
  • In electrochemistry, the Standard Hydrogen Electrode (SHE) is often used as a reference for measuring the potentials of other electrodes.
  • The potential of SHE is arbitrarily taken as a reference point and is considered to be zero.
  • Thus, independent of the conditions, the potential of SHE is always assumed to be zero.
  • Hence, the correct answer is A) Zero.

MCQs 7:

What is the oxidation state of hydrogen in CaH2?





Topic: Oxidation Numbers in Metal Hydrides

Correct Answer: B) -1

Detailed Hint:
  • Hydrogen typically possesses an oxidation state of +1 in most of its compounds. However, there are exceptions to this rule.
  • When hydrogen forms a binary compound with a metal such as calcium in CaH2, the metal becomes positively charged, and hydrogen takes on a negative oxidation state.
  • This is because metals are more electropositive than hydrogen.
  • Therefore, in CaH2, the oxidation state of Hydrogen is -1. So, the correct answer is B) -1.

Question 8:

Which element has the highest reduction potential?





Topic: Electrochemical Reduction Potential

Correct Answer: D) Fluorine (F2)

Detailed Hint:
  • Reduction potential measures the tendency of a chemical species to acquire electrons and thereby be reduced.
  • Sodium, Hydrogen, and Zinc all can accept electrons to varying degrees, but Fluorine has the highest reduction potential.
  • This is because Fluorine is at the bottom of the electrochemical series and has the least ability to lose an electron but the highest ability to gain an electron.
  • Therefore, the correct answer is D) Fluorine (F2).

Question 9:

Which of the following is a strong electrolyte in its aqueous solution?





Topic: Electrolytes in Aqueous Solutions

Correct Answer: C) Potassium iodide

Detailed Hint:
  • A strong electrolyte is a solute that fully, or almost fully, ionizes or dissociates in a solution.
  • Among the options given, Potassium Iodide (KI) is considered a strong electrolyte because it fully dissociates into potassium (K+) ions and iodide (I-) ions in water.
  • This makes the solution highly conductive of electricity.
  • Therefore, the correct answer is C) Potassium iodide.

Question 10:

What is the oxidation number of carbon in CH2Cl2?





Topic: Oxidation Numbers in Organic Chlorides

Correct Answer: D) 0

Detailed Hint:
  • The oxidation number of an atom in a molecule represents the number of electrons it can lose, gain, or share while forming chemical bonds.
  • In CH2Cl2, Carbon is bonded to two Hydrogen atoms and two Chlorine atoms. The oxidation number of Hydrogen is +1 and Chlorine is -1 in compounds.
  • The overall charge of the molecule is zero, which means the sum of the oxidation states of all atoms in the molecule must be zero.
  • Therefore, given that the total contributions of the Hydrogen and Chlorine atoms balance each other out, the oxidation state of Carbon must be zero. Hence, the correct answer is D) 0.

Question 11:

Which transition represents a transfer of five electrons?





Topic: Electron Transfer in Redox Reactions

Correct Answer: C) MnO4- to Mn+2

Detailed Hint:
  • Redox reactions involve the transfer of electrons from one species to another.
  • In this question, we need to find out which change involves a transfer of five electrons.
  • When MnO4- is converted to Mn+2, the oxidation number of Mn changes from +7 to +2, meaning five electrons are transferred.
  • Therefore, the correct answer is C) MnO4- to Mn+2.

Question 12:

What characterizes a weak electrolyte in solution?





Topic: Behavior of Weak Electrolytes

Correct Answer: B) Partially ionized

Detailed Hint:
  • Electrolytes can be classified as strong or weak depending on their ionization in a solution.
  • A weak electrolyte does not fully ionize in a solution, meaning only a small fraction of the solute dissociates into ions.
  • Unlike a strong electrolyte, which completely dissociates into ions.
  • Thus, the correct answer is B) Partially ionized.

Question 13:

Why are coinage metals Cu, Ag, and Au less reactive?





Topic: Reactivity of Coinage Metals

Correct Answer: B) They exhibit positive reduction potential

Detailed Hint:
  • Metals react differently due to their electron configuration and affinity.
  • Coinage metals such as Copper (Cu), Silver (Ag), and Gold (Au) are less reactive because of their high electron affinity.
  • This characteristic gives them a positive reduction potential, meaning they have a tendency to gain electrons and undergo reduction rather than losing electrons (oxidation).
  • Therefore, the correct answer is B) They exhibit positive reduction potential.

Question 14:

In the electrochemical series, identify the most potent reducing agent.





Topic: Reducing Agents in the Electrochemical Series

Correct Answer: D) Lithium (Li)

Detailed Hint:
  • The ability of an element to act as a reducing agent is determined by its potential to lose electrons, i.e., its oxidation potential.
  • In the given options, Lithium (Li) has the highest tendency to lose electrons, thus making it a strong reducing agent.
  • Therefore, the correct answer is D) Lithium (Li).

Question 15:

Determine the oxidation number of Carbon in Sodium Bicarbonate (NaHCO3).





Topic: Oxidation Numbers in Bicarbonates

Correct Answer: A) +4

Detailed Hint:
  • The oxidation number or state of an atom in a compound represents the number of electrons it can lose, gain, or share while forming chemical bonds.
  • In NaHCO3, the oxidation number of Sodium (Na) is +1, Hydrogen (H) is +1, and Oxygen (O) is -2. These values are assigned based on the general rules for oxidation numbers.
  • The sum of the oxidation states in a neutral compound must equal zero. Hence, solving for Carbon (C), we find that it must have an oxidation state of +4.
  • Therefore, the correct answer is A) +4.

Question 16:

What is the oxidation number of Magnesium in Magnesium Carbonate (MgCO3)?





Topic: Oxidation Numbers in Carbonates

Correct Answer: B) +2

Detailed Hint:
  • In a compound, the oxidation number or state of an atom signifies the number of electrons it can lose, gain, or share while forming chemical bonds.
  • In MgCO3, Magnesium (Mg) gives up two electrons to achieve a stable electron configuration. Therefore, its oxidation number is +2.
  • Thus, the correct answer is B) +2.

Question 17:

The process of electrolysis results in which of the following conditions for the liberated cations and anions from the electrolyte?





Topic: Electrolytic Discharge

Correct Answer: D) Discharged

Detailed Hint:
  • Electrolysis refers to the decomposition of ionic compounds into their constituent elements by passing a direct electric current through them in a fluid state.
  • During electrolysis, cations and anions from the electrolyte are liberated.
  • These freed ions undergo a process known as discharge, where cations get reduced at the cathode and anions get oxidized at the anode.
  • Therefore, the correct answer is D) Discharged.

Question 18:

In an electrochemical cell, the element acting as anode usually occupies which position?





Topic: Position of Anode in Electrochemical Cell

Correct Answer: A) Higher

Detailed Hint:
  • In an electrochemical cell, the anode is the electrode where oxidation occurs.
  • An element with a lower standard reduction potential tends to oxidize more readily.
  • Therefore, the element that acts as an anode is usually found in a higher position in the electrochemical series.
  • Thus, the correct answer is A) Higher.

Question 19:

What type of reaction occurs at the cathode during the electrolysis of dilute H2SO4 with a Platinum (Pt) electrode?





Topic: Cathode Reactions in Electrolysis

Correct Answer: A) Reduction

Detailed Hint:
  • Electrolysis involves two types of reactions: oxidation occurs at the anode and reduction at the cathode.
  • When dilute H2SO4 undergoes electrolysis with Pt electrodes, Hydrogen (H2) gas is generated at the cathode due to a reduction reaction.
  • Hence, the correct answer is A) Reduction.

Question 20:

What is the oxidation number of Chlorine (Cl) in Chloric acid (HClO3)?





Topic: Oxidation Numbers in Chloric Acid

Correct Answer: D) +5

Detailed Hint:
  • The oxidation number or state of an atom in a compound signifies the number of electrons it can lose, gain, or share during the formation of chemical bonds.
  • In HClO3, Hydrogen (H) has an oxidation number of +1, and Oxygen (O) has an oxidation number of -2, as per the general rules for oxidation numbers.
  • With the sum of the oxidation states in a neutral compound equating to zero, we solve for Chlorine (Cl) and find that it has an oxidation state of +5.
  • Thus, the correct answer is D) +5.

Question 21:

Which element has the highest oxidation number?





Topic: Maximum Oxidation Numbers

Correct Answer: D) Manganese (Mn)

Detailed Hint:
  • An element's oxidation number represents its capacity to lose, gain, or share electrons during chemical bonding.
  • Manganese (Mn) displays multiple oxidation states, ranging from +1 to +7.
  • Consequently, it possesses the highest oxidation state of +7 among the listed elements.
  • Therefore, the correct answer is D) Manganese (Mn).

Question 22:

What is the term for a decrease in oxidation number?





Topic: Oxidation Numbers and Reduction

Correct Answer: B) Reduction

Detailed Hints:
  • In the realm of chemistry, oxidation states or numbers are used to track electron movement in chemical reactions.
  • A decrease in an element's oxidation number during a reaction implies that it has gained electrons.
  • This process is referred to as reduction.
  • Hence, the correct answer is B) Reduction.

Question 23:

Why does a Zinc (Zn) rod function as an anode in a Daniell cell but as a cathode when coupled with an Aluminum (Al) electrode?





Topic: Zinc's Role in Electrochemical Cells

Correct Answer: A) Zn has a greater standard reduction potential than Al

Detailed Hints:
  • In an electrochemical cell, the electrode with a lower standard reduction potential typically acts as the anode, where oxidation occurs.
  • The behavior of Zinc (Zn) varies based on the electrode it is paired with due to differences in standard reduction potential.
  • When paired with Aluminum (Al), Zn serves as the cathode because its standard reduction potential is greater.
  • Thus, the correct answer is A) Zn has a greater standard reduction potential than Al.

Question 24:

What is a true statement regarding the standard hydrogen electrode (SHE)?





Topic: Standard Hydrogen Electrode

Correct Answer: B) Its reduction potential is zero or negative

Detailed Hints:
  • The standard hydrogen electrode (SHE) is a key reference point in electrochemistry.
  • It has a standard reduction potential (E°red) of zero volts, making it a benchmark for measuring the redox potentials of other substances.
  • SHE's role (anode or cathode) in a galvanic cell depends on the other electrode it's connected with.
  • Therefore, the correct answer is B) Its reduction potential is zero or negative.

Question 25:

Which electrode is used to measure the standard electrode potential of Zinc (Zn)?





Topic: Measuring Standard Electrode Potential

Correct Answer: A) Standard Hydrogen Electrode (SHE)

Detailed Hints:
  • The standard electrode potential (E°) is a measure of the propensity of a substance to lose or gain electrons - or its reducing or oxidizing power.
  • The standard hydrogen electrode (SHE) is commonly used as a reference electrode to measure E° due to its defined potential of zero volts.
  • Therefore, to measure the standard electrode potential of Zinc (Zn), it would be coupled with SHE.
  • Hence, the correct answer is A) Standard Hydrogen Electrode (SHE).

Question 26:

What is the oxidation state of Sulphur (S) in H2SO4?





Topic: Oxidation Numbers in Chemical Compounds

Correct Answer: A) +6

Detailed Hints:
  • In chemical compounds, the oxidation number of an atom represents the total number of electrons that it has lost or gained.
  • For H2SO4, if we assign oxidation numbers to hydrogen (H) as +1 and oxygen (O) as -2, the equation to find out Sulfur's oxidation number becomes: 2(+1) + S + 4(-2) = 0.
  • Solving this equation results in S = +6, indicating that in H2SO4, Sulphur has an oxidation number of +6.
  • Thus, the correct answer is A) +6.

Question 27:

What are the oxidation numbers of oxygen in OF2 and H2O2 respectively?





Topic: Variation of Oxidation Numbers

Correct Answer: B) +2, -1

Detailed Hints:
  • While the most common oxidation state of Oxygen (O) is -2, it can have other oxidation states depending on the compound.
  • In Oxygen difluoride (OF2), Oxygen has an oxidation state of +2 because Fluorine (F) has a higher electronegativity.
  • In Hydrogen peroxide (H2O2), each Oxygen atom has an oxidation state of -1 due to the peroxide linkage.
  • Therefore, the correct answer is B) +2, -1.

Question 28:

At what temperature is the standard electrode potential measured?





Topic: Standard Electrode Potential

Correct Answer: A) 298K

Detailed Hints:
  • The standard electrode potential is measured under standard conditions, which include a pressure of 1 atm, a concentration of 1M, and a specific temperature.
  • By convention, the temperature for such measurements is set at 298 Kelvin (K), which is equivalent to 25°C.
  • This standardization allows for consistent comparisons of reduction potentials across different electrodes.
  • Hence, the correct answer is A) 298K.

MCQs 29:

In determining the standard electrode potential, which solution should Zinc (Zn) be immersed in?





Topic: Standard Electrode Potential Measurement

Correct Answer: B) 1M ZnSO4 solution

Detailed Hint:
  • The standard electrode potential of a substance is determined under specific conditions, including a concentration of 1M.
  • Zinc (Zn) must be immersed in a solution of its salt to measure its standard electrode potential.
  • Among the options, only a 1M solution of ZnSO4 meets the standard conditions.
  • Therefore, the correct answer is B) 1M ZnSO4 solution.

MCQs 30:

How does the reduction potential at a cathode compare to that at an anode?





Topic: Electrochemical Cell Dynamics

Correct Answer: B) More than the anode

Detailed Hint:
  • In an electrochemical cell, the anode is the site of oxidation (loss of electrons) and the cathode is the site of reduction (gain of electrons).
  • Consequently, the reduction potential at the cathode is higher because it attracts electrons more strongly.
  • This difference in potentials drives the flow of electrons from the anode to the cathode.
  • Thus, the correct answer is B) More than the anode.

MCQs 31:

In which compound does Sulphur (S) possess the highest oxidation state?





Topic: Oxidation States in Different Compounds

Correct Answer: B) SO3

Detailed Hint:
  • The oxidation state of an element in a compound is determined by the number of electrons it loses or gains during chemical bonding.
  • For sulfur (S), the number of oxygen atoms attached to it directly influences its oxidation state.
  • Sulfur trioxide (SO3) has the most oxygen atoms bound to each sulfur atom, hence sulfur has the highest oxidation state in this compound.
  • Consequently, the correct answer is B) SO3.

MCQs 32:

During electrolysis of molten NaCl, the ion is reduced is:





Topic: Electrolysis Process

Correct Answer: B) Na+

Detailed Hint:
  • Electrolysis is a chemical process that uses an electric current to drive a non-spontaneous reaction.
  • During the electrolysis of molten NaCl, Sodium ions (Na +) are reduced to Sodium metal at the cathode.
  • This process is an efficient method for producing Sodium metal on a large scale.
  • Therefore, the correct answer is B) Na+.

MCQs 33:

In a glucose molecule, which element has an oxidation state of zero?





Topic: Oxidation State in Glucose

Correct Answer: A) Carbon (C)

Detailed Hint:
  • The formula for glucose is C6H12O6.
  • Applying the oxidation state formula, we find that the oxidation state of Carbon (C) is zero.
  • Hence, the correct answer is A) Carbon (C).

MCQs 34:

Which of the following is another term for the standard electrode potential?





Topic: Standard Electrode Potential Terminology

Correct Answer: C) Standard reduction potential

Detailed Hint:
  • The standard electrode potential is a key term in electrochemistry, helping to predict the direction of redox reactions.
  • This term is also known as the standard reduction potential.
  • Therefore, the correct answer is C) Standard reduction potential.

MCQs 35:

What type of reaction occurs at the anode?





Topic: Anode Reaction Type

Correct Answer: A) Oxidation

Detailed Hint:
  • An electrochemical cell consists of two electrodes: an anode and a cathode.
  • Oxidation, or the loss of electrons, occurs at the anode.
  • Therefore, the correct answer is A) Oxidation.
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