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Saarland Abitur Chemistry practice questions

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Question 1Organic chemistry and macromolecules

What is the general formula for alkanes, the simplest class of hydrocarbons?

  1. CnH2n+2 Correct answer.
  2. CnH2n
  3. CnH2n-2
  4. CnHn

Explanation

Alkanes are saturated hydrocarbons with the general formula CnH2n+2, containing only single bonds between carbon atoms (e.g., methane CH4, ethane C2H6).

Question 2Organic chemistry and macromolecules

What functional group characterizes an 'Alkohol' (alcohol) in organic chemistry?

  1. A hydroxyl group (-OH) attached to a carbon atom Correct answer.
  2. A carbonyl group (C=O) with no oxygen-hydrogen bond
  3. A carboxyl group (-COOH)
  4. An amino group (-NH2)

Explanation

Alcohols are characterized by a hydroxyl functional group (-OH) attached to a saturated carbon atom, as in ethanol (C2H5OH).

Question 3Organic chemistry and macromolecules

What functional group characterizes a 'Carbonsäure' (carboxylic acid)?

  1. A carboxyl group (-COOH) Correct answer.
  2. A hydroxyl group (-OH) alone
  3. An ester group (-COO-)
  4. An aldehyde group (-CHO)

Explanation

Carboxylic acids are characterized by a carboxyl functional group (-COOH), combining a carbonyl and hydroxyl group, as in acetic acid (CH3COOH).

Question 4Organic chemistry and macromolecules

What is an 'Ester', and how is it formed?

  1. A compound formed from the reaction of a carboxylic acid with an alcohol, releasing water (Veresterung) Correct answer.
  2. A compound formed exclusively from two alcohols reacting together
  3. A term unrelated to organic chemistry reactions
  4. A compound that cannot be broken down or hydrolyzed under any conditions

Explanation

An ester is formed through the reaction (Veresterung/esterification) of a carboxylic acid with an alcohol, releasing water as a byproduct, producing a characteristic -COO- linkage often associated with fruity odors.

Question 5Organic chemistry and macromolecules

What is 'Isomerie' (isomerism) in organic chemistry?

  1. The phenomenon where two or more compounds have the same molecular formula but different structural arrangements Correct answer.
  2. A phenomenon where two compounds have completely different molecular formulas and no structural relationship
  3. A term unrelated to organic molecular structure
  4. A phenomenon that only applies to inorganic compounds, never organic ones

Explanation

Isomerism is the phenomenon where two or more compounds share the same molecular formula but have different structural arrangements of atoms, resulting in distinct chemical and/or physical properties (e.g., structural isomers, stereoisomers).

Question 6Organic chemistry and macromolecules

What is the correct IUPAC name for the simplest alkane, CH4?

  1. Methan (methane) Correct answer.
  2. Ethan (ethane)
  3. Propan (propane)
  4. Butan (butane)

Explanation

CH4, the simplest alkane with a single carbon atom, is named Methan (methane) under IUPAC nomenclature.

Question 7Organic chemistry and macromolecules

What is a 'Polymer' in organic/macromolecular chemistry?

  1. A large molecule composed of many repeating smaller units (monomers) chemically bonded together Correct answer.
  2. A single small molecule with no repeating structure
  3. A term unrelated to molecular structure
  4. A molecule that can only exist in a gaseous state

Explanation

A polymer is a large molecule (macromolecule) composed of many repeating smaller structural units called monomers, chemically bonded together in a chain or network, such as polyethylene formed from ethylene monomers.

Question 8Organic chemistry and macromolecules

What is 'Polymerisation' (polymerization), the process forming a polymer?

  1. A chemical process in which many small monomer molecules combine to form a large polymer chain Correct answer.
  2. A process that breaks a large polymer down into individual monomers
  3. A term unrelated to macromolecular chemistry
  4. A process that can only occur at extremely low temperatures near absolute zero

Explanation

Polymerization is the chemical process in which many small monomer molecules chemically combine (through addition or condensation mechanisms) to form a large polymer chain or network.

Question 9Organic chemistry and macromolecules

What is a 'Benzolring' (benzene ring), a foundational structure in aromatic organic chemistry?

  1. A six-carbon ring structure with delocalized pi electrons, exhibiting special stability (aromaticity) Correct answer.
  2. A straight-chain structure with no ring formation
  3. A term unrelated to organic chemistry
  4. A structure that is highly unstable and reacts explosively with any substance

Explanation

A benzene ring is a six-carbon ring structure (C6H6) with delocalized pi electrons distributed around the ring, exhibiting special chemical stability known as aromaticity, a foundational structure in aromatic organic chemistry.

Question 10Organic chemistry and macromolecules

What is a 'Substitutionsreaktion' (substitution reaction) in organic chemistry?

  1. A reaction in which one atom or functional group in a molecule is replaced by another atom or group Correct answer.
  2. A reaction where two molecules simply combine with no atoms replaced
  3. A term unrelated to organic reaction mechanisms
  4. A reaction that can only occur with inorganic compounds

Explanation

A substitution reaction is a reaction in which one atom or functional group within a molecule is replaced by another atom or functional group, common in both aliphatic (e.g., halogenation of alkanes) and aromatic organic chemistry.

Question 11Organic chemistry and macromolecules

What is the correct meaning of 'Elektronegativität' (electronegativity), relevant to predicting bond polarity?

  1. A measure of an atom's tendency to attract shared electrons in a chemical bond Correct answer.
  2. A measure of an atom's total number of protons only, unrelated to bonding
  3. A term unrelated to chemical bonding
  4. A quantity that is identical for every element on the periodic table

Explanation

Electronegativity is a measure of an atom's tendency to attract shared electrons toward itself in a chemical bond, used to predict bond polarity (polar vs. nonpolar covalent, or ionic character).

Question 12Organic chemistry and macromolecules

What is a 'Amid' (amide) functional group, relevant to protein chemistry (peptide bonds)?

  1. A functional group formed from a carboxylic acid and an amine, containing a C(=O)-N bond Correct answer.
  2. A functional group containing only a hydroxyl group with no nitrogen
  3. A term unrelated to nitrogen-containing organic compounds
  4. A functional group that never occurs in biological molecules

Explanation

An amide is a functional group formed from the reaction of a carboxylic acid and an amine, containing a characteristic C(=O)-N bond; the peptide bond linking amino acids in proteins is a specific type of amide bond.

Question 13Organic chemistry and macromolecules

What is an 'Amin' (amine) functional group?

  1. A functional group derived from ammonia, containing a nitrogen atom bonded to one or more carbon groups Correct answer.
  2. A functional group containing only oxygen and hydrogen atoms
  3. A term unrelated to nitrogen chemistry
  4. A functional group that cannot act as a base

Explanation

An amine is a functional group derived structurally from ammonia (NH3), containing a nitrogen atom bonded to one or more carbon (alkyl or aryl) groups, and amines characteristically act as weak bases due to nitrogen's lone electron pair.

Question 14Organic chemistry and macromolecules

What is the correct meaning of 'Additionsreaktion' (addition reaction) in organic chemistry, typical of alkenes?

  1. A reaction in which atoms are added across a double or triple bond, converting it to a single bond Correct answer.
  2. A reaction in which one atom is simply replaced by another with no bond-type change
  3. A term unrelated to organic reaction mechanisms
  4. A reaction that can only occur with saturated (single-bond only) compounds

Explanation

An addition reaction involves atoms being added across a double or triple bond (converting it to a single bond, or a double bond to a single bond respectively), typical of alkenes and alkynes, such as the addition of bromine (Br2) across a double bond.

Question 15Organic chemistry and macromolecules

What is the correct meaning of 'Mesomerie' (resonance), relevant to describing structures like the benzene ring's electron distribution?

  1. A concept describing a molecule's actual electronic structure as a hybrid of multiple contributing structural representations Correct answer.
  2. A concept describing a molecule that physically alternates rapidly between distinct structures over time
  3. A term unrelated to molecular bonding
  4. A concept that applies only to inorganic ions, never organic molecules

Explanation

Mesomerie (resonance) describes how a molecule's actual electronic structure (like delocalized electrons in benzene) is best represented as a hybrid of multiple contributing Lewis structures ('resonance structures'), not that the molecule physically switches between distinct forms over time.

Question 16Organic chemistry and macromolecules

What is the correct IUPAC name for the branched alkane with structure (CH3)3CH (a central carbon bonded to three methyl groups and one hydrogen)?

  1. 2-Methylpropan (isobutane) Correct answer.
  2. n-Butan
  3. 2,2-Dimethylpropan
  4. Propan

Explanation

(CH3)3CH has a four-carbon backbone (propane, C3) with a methyl branch on carbon 2, correctly named 2-Methylpropan (commonly known as isobutane).

Question 17Organic chemistry and macromolecules

What distinguishes a 'primärer Alkohol' (primary alcohol) from a 'sekundärer Alkohol' (secondary alcohol)?

  1. In a primary alcohol, the carbon bearing the -OH group is attached to only one other carbon atom; in a secondary alcohol, it is attached to two Correct answer.
  2. In a primary alcohol, the carbon bearing the -OH group is attached to three other carbons; in a secondary alcohol, to only one
  3. There is no structural distinction between primary and secondary alcohols
  4. Primary alcohols always contain a benzene ring, while secondary alcohols never do

Explanation

In a primary alcohol, the carbon bearing the -OH group is bonded to only ONE other carbon atom (e.g., ethanol); in a secondary alcohol, that carbon is bonded to TWO other carbon atoms (e.g., isopropanol/2-propanol).

Question 18Organic chemistry and macromolecules

When a primary alcohol (e.g., ethanol) is oxidized with an appropriate oxidizing agent, what is the typical product sequence?

  1. The alcohol is first oxidized to an aldehyde, then further oxidized to a carboxylic acid Correct answer.
  2. The alcohol is directly and only oxidized to a ketone, with no further reaction possible
  3. Primary alcohols cannot be oxidized under any conditions
  4. The alcohol is reduced (not oxidized) to an alkane

Explanation

A primary alcohol (like ethanol) is first oxidized to an aldehyde (e.g., ethanal), and with excess oxidizing agent, the aldehyde is further oxidized to a carboxylic acid (e.g., ethanoic/acetic acid).

Question 19Organic chemistry and macromolecules

What product forms when a secondary alcohol (e.g., propan-2-ol) is oxidized with an appropriate oxidizing agent?

  1. A ketone (e.g., propanone/acetone) Correct answer.
  2. An aldehyde, identical to the product from primary alcohol oxidation
  3. A carboxylic acid, with no possibility of an intermediate product
  4. No reaction occurs; secondary alcohols cannot be oxidized

Explanation

Oxidation of a secondary alcohol (like propan-2-ol) produces a ketone (propanone/acetone), since the carbon bearing the -OH has only one hydrogen to lose and no further oxidation to a carboxylic acid is possible under normal conditions.

Question 20Organic chemistry and macromolecules

Why do tertiary alcohols (e.g., 2-methylpropan-2-ol) generally resist oxidation by common oxidizing agents like acidified potassium dichromate?

  1. The carbon bearing the -OH group has no hydrogen atom attached, so it cannot lose a hydrogen to form a carbonyl (C=O) group Correct answer.
  2. Tertiary alcohols do not actually contain an -OH group at all
  3. Tertiary alcohols react so violently that oxidation is simply too dangerous to attempt
  4. Tertiary alcohols spontaneously combust before any oxidizing agent can be added

Explanation

In a tertiary alcohol, the carbon bearing the -OH group is bonded to three other carbon atoms and has NO hydrogen atom attached to it; since oxidation to a carbonyl (C=O) group requires removing a hydrogen from that specific carbon, tertiary alcohols cannot undergo this oxidation under normal conditions.

Question 21Organic chemistry and macromolecules

What is an 'Eliminierungsreaktion' (elimination reaction), such as the dehydrohalogenation of a haloalkane?

  1. A reaction in which atoms or groups are removed from a molecule, typically forming a double bond and a small byproduct like HBr Correct answer.
  2. A reaction in which atoms are added across an existing double bond
  3. A term unrelated to organic reaction mechanisms
  4. A reaction that can only occur with alkanes containing no halogen substituents

Explanation

An elimination reaction removes atoms or groups from a molecule (e.g., a hydrogen and a halogen from adjacent carbons in a haloalkane), typically forming a double bond in the main product along with a small byproduct like HBr, as in dehydrohalogenation with a strong base.

Question 22Organic chemistry and macromolecules

In the radical chain mechanism of addition polymerization (e.g., forming polyethylene from ethylene), what are the three key stages, in order?

  1. Initiation (radical formation), propagation (chain growth), termination (chain ends combine) Correct answer.
  2. Oxidation, reduction, and neutralization
  3. Melting, evaporation, and condensation
  4. Dissolution, precipitation, and filtration

Explanation

The radical chain mechanism of addition polymerization proceeds through three stages: initiation (an initiator forms reactive radicals), propagation (radicals repeatedly add to monomers, extending the chain), and termination (two radical chain ends combine, ending chain growth).

Question 23Organic chemistry and macromolecules

How does a 'Polyester' (polyester) condensation polymer form from its monomers?

  1. Through repeated esterification reactions between a dicarboxylic acid and a diol, releasing water at each linkage Correct answer.
  2. Through simple addition of monomers across double bonds with no small molecule released
  3. A term unrelated to condensation polymer chemistry
  4. Through a reaction that can only occur between two identical alcohol monomers

Explanation

A polyester forms through repeated esterification (condensation) reactions between a dicarboxylic acid monomer and a diol monomer, releasing water at each new ester linkage formed, building up a long polymer chain.

Question 24Organic chemistry and macromolecules

How is a 'Polyamid' (polyamide, e.g., nylon) structurally related to proteins, in terms of the bond linking monomer units?

  1. Both polyamides and proteins are linked by amide bonds, formed between a carboxyl group and an amine group Correct answer.
  2. Polyamides and proteins share no structural similarity whatsoever
  3. Both are linked exclusively by ester bonds, identical to polyesters
  4. Both are linked by simple carbon-carbon single bonds with no functional group involved

Explanation

Both synthetic polyamides (like nylon) and natural proteins are linked by amide bonds - in proteins specifically called peptide bonds - formed through condensation reactions between a carboxyl group (-COOH) and an amine group (-NH2), releasing water.

Question 25Organic chemistry and macromolecules

What is a 'chirales Zentrum' (chiral center/stereocenter), relevant to optical isomerism?

  1. A carbon atom bonded to four different substituent groups, giving rise to two non-superimposable mirror-image forms Correct answer.
  2. A carbon atom bonded to four identical substituent groups
  3. A term unrelated to molecular structure or isomerism
  4. A property that can only occur in inorganic ionic compounds

Explanation

A chiral center (stereocenter) is a carbon atom bonded to four DIFFERENT substituent groups, giving rise to two non-superimposable mirror-image forms (enantiomers) - a key concept in optical isomerism, relevant to biomolecules like amino acids and sugars.

Question 26Organic chemistry and macromolecules

What is the correct chemical description of dietary 'Fette' (fats), relevant to organic chemistry's ester functional group?

  1. Fats are esters formed from glycerol (a triol) and three fatty acid molecules (triglycerides) Correct answer.
  2. Fats are simple hydrocarbons with no oxygen-containing functional group
  3. Fats are inorganic salts with no carbon content
  4. Fats are identical in structure to simple carbohydrates like glucose

Explanation

Dietary fats (triglycerides) are esters formed from glycerol (a three-carbon triol) and three fatty acid molecules, each fatty acid's carboxyl group esterifying with one of glycerol's three hydroxyl groups, releasing three water molecules.

Question 27Physical chemistry, amounts and reactions

What is 'Oxidationszahl' (oxidation number/state) in redox chemistry?

  1. A number assigned to an atom in a compound representing the hypothetical charge it would have if all bonds were fully ionic Correct answer.
  2. A number that is always identical to an atom's total electron count
  3. A term unrelated to redox chemistry
  4. A number that never changes during any chemical reaction

Explanation

Oxidation number (Oxidationszahl) is a number assigned to an atom in a compound representing the hypothetical charge it would have if all bonds to that atom were considered fully ionic, a bookkeeping tool essential for tracking electron transfer in redox reactions.

Question 28Physical chemistry, amounts and reactions

What is 'Oxidation' in redox chemistry terms, defined via electron transfer?

  1. A loss of electrons by a substance, resulting in an increase in oxidation number Correct answer.
  2. A gain of electrons by a substance, resulting in a decrease in oxidation number
  3. A term unrelated to electron transfer
  4. A process that always involves oxygen directly, with no other possible mechanism

Explanation

Oxidation is defined as the LOSS of electrons by a substance, resulting in an INCREASE in that substance's oxidation number (a mnemonic: 'OIL' - Oxidation Is Loss).

Question 29Physical chemistry, amounts and reactions

What is 'Reduktion' (reduction) in redox chemistry terms?

  1. A gain of electrons by a substance, resulting in a decrease in oxidation number Correct answer.
  2. A loss of electrons by a substance, resulting in an increase in oxidation number
  3. A term unrelated to electron transfer
  4. A process that only occurs in biological systems, never in general chemistry

Explanation

Reduction is defined as the GAIN of electrons by a substance, resulting in a DECREASE in that substance's oxidation number (following the 'OIL RIG' mnemonic: Reduction Is Gain).

Question 30Physical chemistry, amounts and reactions

What is a 'galvanische Zelle' (galvanic/voltaic cell)?

  1. An electrochemical cell that converts chemical energy into electrical energy through a spontaneous redox reaction Correct answer.
  2. A cell that requires an external electrical power source to drive a non-spontaneous reaction
  3. A term unrelated to electrochemistry
  4. A cell that can only be constructed using pure water with no electrolyte

Explanation

A galvanic (voltaic) cell is an electrochemical cell that converts chemical energy into electrical energy through a SPONTANEOUS redox reaction, generating a voltage/current - the basic principle of batteries.

Question 31Physical chemistry, amounts and reactions

What is 'Elektrolyse' (electrolysis)?

  1. A process using electrical energy to drive a non-spontaneous chemical reaction Correct answer.
  2. A process that generates electrical energy from a spontaneous chemical reaction
  3. A term unrelated to electrochemistry
  4. A process that can occur with no electrical current involved at all

Explanation

Electrolysis is a process using externally supplied electrical energy to drive a non-spontaneous chemical reaction, such as decomposing water into hydrogen and oxygen gas, occurring in an electrolytic cell.

Question 32Physical chemistry, amounts and reactions

What is an 'Elektrode' (electrode) in an electrochemical cell?

  1. A conductor through which electric current enters or leaves an electrochemical cell, where oxidation or reduction reactions occur Correct answer.
  2. A term for the entire electrochemical cell, with no distinct meaning
  3. An insulating material that blocks all current flow
  4. A term unrelated to electrochemistry

Explanation

An electrode is a conductor (often a metal) through which electric current enters or leaves an electrochemical cell, serving as the site where oxidation (at the anode) or reduction (at the cathode) reactions occur.

Question 33Physical chemistry, amounts and reactions

Which half-reaction correctly represents the oxidation of Fe²⁺ to Fe³⁺?

  1. Fe²⁺ → Fe³⁺ + e⁻ Correct answer.
  2. Fe³⁺ + e⁻ → Fe²⁺
  3. Fe²⁺ + e⁻ → Fe³⁺
  4. Fe³⁺ → Fe²⁺ + e⁻

Explanation

Oxidation of Fe²⁺ to Fe³⁺ involves the LOSS of one electron: Fe²⁺ → Fe³⁺ + e⁻, correctly balanced for both charge and mass.

Question 34Physical chemistry, amounts and reactions

What is a 'Standardelektrodenpotential' (standard electrode potential, E°)?

  1. A measured voltage indicating a half-cell's tendency to be reduced, relative to the standard hydrogen electrode (defined as 0 V) Correct answer.
  2. A measure of a solution's pH under standard conditions
  3. A term unrelated to electrochemistry
  4. A value that is identical for every metal electrode

Explanation

Standard electrode potential (E°) is a measured voltage indicating a half-cell's tendency to be reduced, measured relative to the standard hydrogen electrode (defined as exactly 0 V) under standard conditions (1 mol/L, 298 K, 1 bar).

Question 35Physical chemistry, amounts and reactions

A half-cell has a more positive standard electrode potential than another. What does this indicate about its relative behavior?

  1. It has a greater tendency to be reduced, making it a stronger oxidizing agent Correct answer.
  2. It has a greater tendency to be oxidized, making it a stronger reducing agent
  3. No conclusion about relative behavior can be drawn from E° values
  4. It indicates the half-cell contains no metal at all

Explanation

A more positive standard electrode potential indicates a greater tendency for the species to be REDUCED (gain electrons), meaning it acts as a stronger oxidizing agent relative to species with lower E° values.

Question 36Physical chemistry, amounts and reactions

In a classic Daniell cell (Zn/Zn²⁺ and Cu/Cu²⁺ half-cells), which electrode serves as the anode?

  1. The zinc electrode, since zinc is oxidized (has a more negative standard electrode potential than copper) Correct answer.
  2. The copper electrode, since copper is oxidized
  3. Neither electrode, since no oxidation occurs in a Daniell cell
  4. Both electrodes simultaneously serve as the anode

Explanation

In a Daniell cell, zinc (E° = -0.76 V) has a more negative standard electrode potential than copper (E° = +0.34 V), so zinc is oxidized (Zn → Zn²⁺ + 2e⁻) at the anode, while copper ions are reduced at the cathode.

Question 37Physical chemistry, amounts and reactions

For a Daniell cell with E°(Cu²⁺/Cu) = +0.34 V and E°(Zn²⁺/Zn) = -0.76 V, what is the standard cell potential (E°cell)?

  1. +1.10 V, since E°cell = E°cathode - E°anode = 0.34 - (-0.76) Correct answer.
  2. +0.42 V, adding the two values directly with signs kept
  3. -1.10 V, reversing the correct sign
  4. +0.76 V, using only the zinc value

Explanation

E°cell = E°cathode - E°anode = E°(Cu²⁺/Cu) - E°(Zn²⁺/Zn) = 0.34 V - (-0.76 V) = 0.34 + 0.76 = 1.10 V.

Question 38Physical chemistry, amounts and reactions

What does a positive standard cell potential (E°cell > 0) indicate about a galvanic cell's reaction?

  1. The reaction is thermodynamically spontaneous under standard conditions Correct answer.
  2. The reaction is thermodynamically non-spontaneous under standard conditions
  3. E°cell has no relationship to reaction spontaneity
  4. The reaction can only proceed if heated to boiling

Explanation

A positive standard cell potential (E°cell > 0) indicates that the overall redox reaction is thermodynamically SPONTANEOUS under standard conditions, consistent with the relationship ΔG° = -nFE°cell (negative ΔG° for positive E°cell).

Question 39Physical chemistry, amounts and reactions

What is a 'Disproportionierung' (disproportionation reaction) in redox chemistry?

  1. A reaction in which a single element in one oxidation state is simultaneously oxidized and reduced, forming two different products Correct answer.
  2. A reaction in which two different elements are both oxidized simultaneously
  3. A term unrelated to redox chemistry
  4. A reaction that can never occur with chlorine or its compounds

Explanation

Disproportionation is a reaction in which a single element in one oxidation state is simultaneously oxidized AND reduced, forming two different products with different oxidation states, such as Cl2 reacting with water to form both Cl⁻ (reduced) and OCl⁻/HOCl (oxidized).

Question 40Physical chemistry, amounts and reactions

In the electrochemical series, where are the strongest reducing agents typically located?

  1. At the top, associated with metals having the most negative standard electrode potentials (e.g., alkali metals) Correct answer.
  2. At the bottom, associated with the most positive standard electrode potentials
  3. Reducing agent strength cannot be determined from the electrochemical series
  4. Only at the exact midpoint of the series, regardless of specific E° values

Explanation

The strongest reducing agents are located at the top of the electrochemical series, associated with the most NEGATIVE standard electrode potentials (e.g., alkali and alkaline earth metals like Li, K, Ca), which readily lose electrons.

Question 41Physical chemistry, amounts and reactions

Balance the redox equation: MnO4⁻ + Fe²⁺ + H⁺ → Mn²⁺ + Fe³⁺ + H2O. What are the correct coefficients (in the order written)?

  1. 1 MnO4⁻ + 5 Fe²⁺ + 8 H⁺ → 1 Mn²⁺ + 5 Fe³⁺ + 4 H2O Correct answer.
  2. 1 MnO4⁻ + 1 Fe²⁺ + 1 H⁺ → 1 Mn²⁺ + 1 Fe³⁺ + 1 H2O
  3. 2 MnO4⁻ + 5 Fe²⁺ + 8 H⁺ → 2 Mn²⁺ + 5 Fe³⁺ + 4 H2O
  4. 1 MnO4⁻ + 5 Fe²⁺ + 4 H⁺ → 1 Mn²⁺ + 5 Fe³⁺ + 8 H2O

Explanation

Balancing via half-reactions: MnO4⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H2O (reduction, Mn goes +7→+2, gaining 5 electrons) combined with 5×(Fe²⁺ → Fe³⁺ + e⁻) (oxidation) gives the balanced equation: MnO4⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H2O.

Question 42Physical chemistry, amounts and reactions

Using Faraday's law, how much copper (molar mass 63.5 g/mol) is deposited by a current of 2 A flowing for 9650 seconds during electrolysis of CuSO4 solution (Faraday constant F ≈ 96500 C/mol, Cu²⁺ + 2e⁻ → Cu)?

  1. approximately 6.35 g, since Q=It=19300 C, n(e⁻)=Q/F=0.2 mol, n(Cu)=0.1 mol, m=0.1×63.5 Correct answer.
  2. approximately 63.5 g, using the full molar mass with no charge calculation
  3. approximately 12.7 g, doubling the correct result unnecessarily
  4. approximately 3.175 g, halving the correct result unnecessarily

Explanation

Q = I×t = 2 A × 9650 s = 19300 C. Moles of electrons = Q/F = 19300/96500 = 0.2 mol e⁻. Since Cu²⁺ requires 2 electrons per atom, moles of Cu = 0.2/2 = 0.1 mol. Mass = 0.1 mol × 63.5 g/mol = 6.35 g.

Question 43Physical chemistry, amounts and reactions

What is the approximate value of the Faraday constant (F)?

  1. approximately 96500 C/mol (coulombs per mole of electrons) Correct answer.
  2. approximately 6.022×10²³ C/mol
  3. approximately 22.4 C/mol
  4. approximately 1.6×10⁻¹⁹ C/mol

Explanation

The Faraday constant (F) is approximately 96500 C/mol, representing the electric charge carried by one mole of electrons (F = Avogadro's number × elementary charge).

Question 44Physical chemistry, amounts and reactions

What are the products formed at the electrodes during the electrolysis of molten (not aqueous) sodium chloride (NaCl)?

  1. Sodium metal (Na) at the cathode and chlorine gas (Cl2) at the anode Correct answer.
  2. Hydrogen gas at the cathode and oxygen gas at the anode, since water is always involved
  3. Only solid sodium chloride is reformed, with no new products
  4. Chlorine metal at the cathode and sodium gas at the anode

Explanation

In the electrolysis of MOLTEN NaCl (no water present), Na⁺ ions are reduced to sodium metal at the cathode, and Cl⁻ ions are oxidized to chlorine gas at the anode - the basis of the industrial Downs process for sodium production.

Question 45Physical chemistry, amounts and reactions

What type of chemical process is 'Korrosion' (corrosion), such as the rusting of iron?

  1. An electrochemical (redox) process in which a metal is gradually oxidized by environmental oxygen and moisture Correct answer.
  2. A purely physical process with no chemical reaction involved
  3. A term unrelated to redox chemistry
  4. A process that only affects non-metal materials

Explanation

Corrosion (such as iron rusting) is an electrochemical (redox) process in which a metal is gradually oxidized by environmental oxygen and moisture, forming metal oxides/hydroxides (e.g., iron rust, Fe2O3·xH2O).

Question 46Physical chemistry, amounts and reactions

What is 'kathodischer Schutz' (cathodic protection), a technique used to prevent corrosion of metals like iron?

  1. Connecting the metal to a more reactive metal (a sacrificial anode) that is oxidized preferentially, protecting the original metal Correct answer.
  2. Coating the metal exclusively with paint, with no electrochemical component
  3. A term unrelated to corrosion prevention
  4. A technique that accelerates corrosion of the protected metal

Explanation

Cathodic protection connects the metal to be protected (e.g., iron) to a more reactive 'sacrificial anode' metal (e.g., zinc or magnesium), which is preferentially oxidized instead, protecting the original metal from corrosion - commonly used on ship hulls and pipelines.

Question 47Physical chemistry, amounts and reactions

What is the function of a 'Salzbrücke' (salt bridge) in a galvanic cell?

  1. To maintain electrical neutrality by allowing ion flow between the two half-cells, completing the circuit Correct answer.
  2. To directly conduct electrons between the two half-cells
  3. A term unrelated to galvanic cell function
  4. To prevent any current from flowing in the cell

Explanation

A salt bridge maintains electrical neutrality by allowing ions to flow between the two half-cells (compensating for charge buildup as the reaction proceeds), completing the circuit without allowing the solutions to directly mix.

Question 48Physical chemistry, amounts and reactions

What is the 'Standard-Wasserstoffelektrode' (standard hydrogen electrode, SHE) used for in electrochemistry?

  1. It serves as the universal reference point, arbitrarily assigned a standard electrode potential of exactly 0 V Correct answer.
  2. It is the electrode with the highest possible standard electrode potential of any known half-cell
  3. A term unrelated to electrode potential measurement
  4. It can only be used to measure temperature, not voltage

Explanation

The standard hydrogen electrode (SHE) serves as the universal reference point for electrochemistry, arbitrarily assigned a standard electrode potential of exactly 0 V, against which all other standard electrode potentials are measured.

Question 49Physical chemistry, amounts and reactions

What is the pH scale used to measure?

  1. The acidity or alkalinity (basicity) of an aqueous solution, based on hydrogen ion concentration Correct answer.
  2. The temperature of a solution
  3. The color of a solution with no connection to chemical properties
  4. The total mass of a solution

Explanation

The pH scale measures the acidity or alkalinity (basicity) of an aqueous solution, based on the concentration of hydrogen ions (H+), with pH = -log[H+]; pH 7 is neutral, below 7 is acidic, above 7 is basic.

Question 50Physical chemistry, amounts and reactions

What is the formula relating pH to hydrogen ion concentration?

  1. pH = -log[H+] Correct answer.
  2. pH = [H+]
  3. pH = log[H+]
  4. pH = 1/[H+]

Explanation

pH is calculated as pH = -log[H+], the negative base-10 logarithm of the hydrogen ion concentration (in mol/L).