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Abitur Chemistry study materials
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Abitur Chemistry practice questions

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Question 1Physical chemistry, amounts and reactions

What are the products of complete neutralization between hydrochloric acid and sodium hydroxide?

  1. NaCl and H2O Correct answer.
  2. NaH and Cl2O
  3. NaClO and H2
  4. NaOH2 and HCl

Explanation

H+ from the acid reacts with OH- from the base to form water, while Na+ and Cl- remain as sodium chloride in solution.

Question 2Physical chemistry, amounts and reactions

In the reaction Mg(s) + Cu2+(aq) -> Mg2+(aq) + Cu(s), which species is oxidized?

  1. Cu2+
  2. Mg Correct answer.
  3. Mg2+
  4. Cu

Explanation

Magnesium loses two electrons to form Mg2+, so Mg is oxidized. Copper(II) gains electrons and is reduced to Cu metal.

Question 3Physical chemistry, amounts and reactions

A solution with pH 3 has how much greater H+ concentration than a solution with pH 5?

  1. 2 times
  2. 10 times
  3. 100 times Correct answer.
  4. 1000 times

Explanation

Each pH unit represents a factor of 10 in H+ concentration. A difference of 2 pH units means 10^2 = 100 times greater H+ concentration.

Question 4Physical chemistry, amounts and reactions

A weak acid differs from a strong acid because a weak acid:

  1. Contains fewer hydrogen atoms per molecule
  2. Partially dissociates in water Correct answer.
  3. Has no conjugate base
  4. Cannot react with hydroxide ions

Explanation

Weak acids establish an equilibrium and only partially donate protons in water. Strength refers to extent of ionization, not concentration or formula alone.

Question 5Physical chemistry, amounts and reactions

At 25 C, the equivalence point of a strong acid-strong base titration is closest to:

  1. pH 1
  2. pH 5
  3. pH 7 Correct answer.
  4. pH 12

Explanation

At equivalence, strong acid and strong base have formed a neutral salt solution, so the pH is about 7 at 25 C.

Question 6Physical chemistry, amounts and reactions

A solution containing similar amounts of ethanoic acid and sodium ethanoate acts as a buffer because it contains:

  1. A strong acid and strong base that fully neutralize
  2. A weak acid and its conjugate base Correct answer.
  3. Only neutral water molecules
  4. An insoluble precipitate that removes H+

Explanation

A buffer contains a weak acid and its conjugate base in appreciable amounts. The pair can consume added OH- or H+ with only small pH changes.

Question 7Physical chemistry, amounts and reactions

What is the pH of 0.010 mol/L HCl, assuming complete dissociation?

  1. 1
  2. 2 Correct answer.
  3. 7
  4. 12

Explanation

HCl is a strong acid, so [H+] = 0.010 mol/L = 10^-2 mol/L. Therefore pH = -log(10^-2) = 2.

Question 8Physical chemistry, amounts and reactions

A solution has pOH = 3.00 at 25 C. What is its pH?

  1. 3.00
  2. 7.00
  3. 11.00 Correct answer.
  4. 17.00

Explanation

At 25 C, pH + pOH = 14.00. Therefore pH = 14.00 - 3.00 = 11.00.

Question 9Physical chemistry, amounts and reactions

For HA(aq) + H2O(l) <-> H3O+(aq) + A-(aq), which expression is Ka?

  1. [HA]/([H3O+][A-])
  2. [H3O+][A-]/[HA] Correct answer.
  3. [H2O][HA]/[A-]
  4. [A-]/[H2O]

Explanation

The acid dissociation constant is products over reactant acid: Ka = [H3O+][A-]/[HA]. Liquid water is omitted from the expression.

Question 10Physical chemistry, amounts and reactions

What is the oxidation number of manganese in MnO4-?

  1. +2
  2. +4
  3. +7 Correct answer.
  4. -1

Explanation

Four oxygens contribute -8 total. The ion charge is -1, so Mn must be +7 because x - 8 = -1.

Question 11Physical chemistry, amounts and reactions

In acidic solution, MnO4- oxidizes Fe2+ to Fe3+ while MnO4- is reduced to Mn2+. How many Fe2+ ions react per MnO4- ion?

  1. 1
  2. 3
  3. 5 Correct answer.
  4. 8

Explanation

Mn changes from +7 to +2, gaining 5 electrons. Each Fe2+ loses 1 electron to become Fe3+, so 5 Fe2+ ions are needed.

Question 12Physical chemistry, amounts and reactions

If acid HA has pKa 3 and acid HB has pKa 6, which statement is correct?

  1. HA is the stronger acid Correct answer.
  2. HB is the stronger acid
  3. They have equal strength because both are weak
  4. pKa does not relate to acid strength

Explanation

Lower pKa means larger Ka and stronger acid. HA with pKa 3 is about 1000 times stronger than HB with pKa 6.

Question 13Physical chemistry, amounts and reactions

A buffer has equal concentrations of a weak acid and its conjugate base. What is its pH?

  1. 0
  2. 7 regardless of acid
  3. Equal to the pKa of the acid Correct answer.
  4. Equal to twice the pKa

Explanation

By the Henderson-Hasselbalch relationship, pH = pKa + log([base]/[acid]). If the concentrations are equal, log(1) = 0, so pH = pKa.

Question 14Physical chemistry, amounts and reactions

At the equivalence point when a weak acid is titrated with a strong base, the pH is usually:

  1. Below 7 because excess acid remains
  2. Exactly 7 because all titrations are neutral
  3. Above 7 because the conjugate base hydrolyzes water Correct answer.
  4. Impossible to estimate from acid-base theory

Explanation

At equivalence, the weak acid has been converted to its conjugate base. That base reacts with water to produce OH-, giving pH above 7.

Question 15Physical chemistry, amounts and reactions

If the molar solubility of AgCl in pure water is 1.3 x 10^-5 mol/L, what is Ksp?

  1. 1.3 x 10^-5
  2. 2.6 x 10^-5
  3. 1.7 x 10^-10 Correct answer.
  4. 1.3 x 10^-10

Explanation

For AgCl(s) <-> Ag+ + Cl-, Ksp = s^2. (1.3 x 10^-5)^2 = 1.69 x 10^-10, about 1.7 x 10^-10.

Question 16Physical chemistry, amounts and reactions

Adding NaCl to a saturated AgCl solution decreases AgCl solubility because of:

  1. The common ion effect Correct answer.
  2. A decrease in temperature only
  3. Formation of sodium metal
  4. A catalyst poisoning effect

Explanation

Added Cl- is common to the AgCl dissolution equilibrium. Increased chloride shifts the equilibrium toward solid AgCl, lowering silver ion solubility.

Question 17Physical chemistry, amounts and reactions

A buffer initially contains 0.10 mol HA and 0.10 mol A-. After 0.020 mol HCl is added, what is the pH if pKa = 4.76?

  1. 4.18
  2. 4.58 Correct answer.
  3. 4.76
  4. 4.94

Explanation

H+ converts A- to HA, leaving 0.080 mol A- and 0.120 mol HA. pH = 4.76 + log(0.080/0.120) = 4.76 + log(0.667) = about 4.58.

Question 18Physical chemistry, amounts and reactions

25.0 mL of 0.100 mol/L ethanoic acid is titrated with 10.0 mL of 0.100 mol/L NaOH. If pKa = 4.76, what is the approximate pH?

  1. 3.00
  2. 4.58 Correct answer.
  3. 4.76
  4. 8.72

Explanation

Initial HA = 2.50 mmol and OH- added = 1.00 mmol. After reaction, HA = 1.50 mmol and A- = 1.00 mmol. pH = 4.76 + log(1.00/1.50) = about 4.58.

Question 19Physical chemistry, amounts and reactions

AgCl has Ksp = 1.8 x 10^-10. What is the approximate molar solubility of AgCl in 0.10 mol/L NaCl?

  1. 1.8 x 10^-9 mol/L Correct answer.
  2. 1.3 x 10^-5 mol/L
  3. 1.8 x 10^-10 mol/L
  4. 1.8 x 10^-11 mol/L

Explanation

In 0.10 mol/L Cl-, Ksp = [Ag+][Cl-] = s(0.10), so s = 1.8 x 10^-10 / 0.10 = 1.8 x 10^-9 mol/L.

Question 20Physical chemistry, amounts and reactions

Given E(Fe3+/Fe2+) = +0.77 V and E(I2/I-) = +0.54 V, what is Estandard for 2Fe3+ + 2I- -> 2Fe2+ + I2?

  1. +0.23 V Correct answer.
  2. -0.23 V
  3. +1.31 V
  4. -1.31 V

Explanation

Fe3+ is reduced, so its reduction potential is the cathode value. I- is oxidized, so Ecell = 0.77 - 0.54 = +0.23 V.

Question 21Organic chemistry and macromolecules

An alkene decolorizes bromine water because bromine undergoes:

  1. Substitution at a saturated carbon
  2. Addition across the C=C double bond Correct answer.
  3. Neutralization with the alkene
  4. Precipitation as bromide salt

Explanation

The pi bond in an alkene reacts with Br2 in an addition reaction, consuming colored bromine and forming a dibromo compound.

Question 22Organic chemistry and macromolecules

An ester is commonly formed by reacting a carboxylic acid with:

  1. An alcohol Correct answer.
  2. An alkane
  3. A noble gas
  4. A metal carbonate only

Explanation

Esterification combines a carboxylic acid and an alcohol, usually with acid catalysis, producing an ester and water.

Question 23Organic chemistry and macromolecules

Controlled oxidation of a primary alcohol can first produce:

  1. An aldehyde Correct answer.
  2. An alkane
  3. An amide
  4. A ketone with the same carbon skeleton

Explanation

Primary alcohols can be oxidized first to aldehydes and then further to carboxylic acids if oxidation continues.

Question 24Organic chemistry and macromolecules

PET is classified as a polyester because its repeating units contain:

  1. Ester linkages Correct answer.
  2. Peptide linkages
  3. Only metallic bonds
  4. Free chloride ions

Explanation

Polyesters contain repeated ester functional groups in the polymer chain. PET is formed from monomers that create these ester linkages.

Question 25Organic chemistry and macromolecules

Acid-catalyzed hydrolysis of ethyl ethanoate produces:

  1. Ethanol and ethanoic acid Correct answer.
  2. Ethene and methanoic acid
  3. Ethanal and sodium ethanoate
  4. Ethane and carbon dioxide

Explanation

Hydrolysis breaks the ester bond, regenerating the alcohol and carboxylic acid: ethyl ethanoate gives ethanol and ethanoic acid.

Question 26Organic chemistry and macromolecules

The major product of adding HBr to propene under normal ionic conditions is:

  1. 1-bromopropane
  2. 2-bromopropane Correct answer.
  3. Propane
  4. 1,2-dibromopropane

Explanation

Markovnikov addition places H on the carbon already bearing more hydrogens, giving the more stable secondary carbocation and then 2-bromopropane.

Question 27Organic chemistry and macromolecules

Polymerization of ethene to polyethene is an addition polymerization because:

  1. Small molecules such as water are eliminated
  2. The C=C bonds open and monomers join without losing atoms Correct answer.
  3. Ester bonds form between monomers
  4. The polymer decomposes into carbon dioxide

Explanation

In addition polymerization, alkene double bonds open and link monomers into a chain. No small molecule is eliminated.

Question 28Organic chemistry and macromolecules

Which compound contains a chiral carbon atom?

  1. Propanone
  2. Ethene
  3. 2-butanol Correct answer.
  4. Methane

Explanation

The second carbon in 2-butanol is bonded to four different groups: H, OH, CH3, and C2H5. That makes it chiral.

Question 29Organic chemistry and macromolecules

A nucleophile is a species that:

  1. Donates an electron pair to an electron-poor center Correct answer.
  2. Accepts an electron pair from a Lewis base
  3. Only removes protons from acids
  4. Always has a positive charge

Explanation

A nucleophile is electron-rich and donates an electron pair, often attacking an electrophilic carbon or other electron-poor atom.

Question 30Organic chemistry and macromolecules

Carboxylic acids often boil higher than comparable aldehydes because carboxylic acids can:

  1. Form hydrogen-bonded dimers Correct answer.
  2. Exist only as ions in pure liquid form
  3. Break all C-C bonds on heating
  4. Have lower molar masses than aldehydes

Explanation

Carboxylic acids can form pairs held by two hydrogen bonds, which greatly increases intermolecular attraction and boiling point.

Question 31Organic chemistry and macromolecules

Benzene tends to undergo substitution rather than addition because addition would:

  1. Destroy aromatic stabilization Correct answer.
  2. Create an ionic lattice
  3. Make the ring more aromatic
  4. Remove all hydrogen atoms from the molecule

Explanation

Addition to benzene would disrupt the delocalized aromatic pi system. Substitution preserves aromatic stabilization after the reaction.

Question 32Organic chemistry and macromolecules

Soap ions help remove grease because they are:

  1. Amphiphilic, with a hydrophilic head and hydrophobic tail Correct answer.
  2. Entirely nonpolar and insoluble in water
  3. Strong oxidizing agents that burn grease
  4. Small noble-gas atoms trapped in water

Explanation

Soap ions have nonpolar hydrocarbon tails that interact with grease and ionic heads that interact with water, allowing micelles to disperse oils.

Question 33Organic chemistry and macromolecules

Chlorination of methane under UV light is classified mainly as:

  1. Electrophilic addition
  2. Free-radical substitution Correct answer.
  3. Esterification
  4. Condensation polymerization

Explanation

UV light initiates homolytic cleavage of Cl2, producing radicals. A hydrogen on methane is substituted by chlorine through a radical chain mechanism.

Question 34Organic chemistry and macromolecules

Which reagent and condition best converts propan-1-ol to propanoic acid in one planned synthesis?

  1. Acidified dichromate under reflux Correct answer.
  2. H2 with nickel catalyst
  3. Bromine water at room temperature
  4. NaBH4 in methanol

Explanation

A primary alcohol can be oxidized fully to a carboxylic acid using acidified dichromate under reflux, which allows continued oxidation beyond the aldehyde.

Question 35Organic chemistry and macromolecules

A compound gives a silver mirror with Tollens' reagent but does not decolorize bromine water by addition. The compound is most likely:

  1. Propanal Correct answer.
  2. Propanone
  3. Propene
  4. Propan-2-ol

Explanation

Tollens' reagent oxidizes aldehydes, giving a silver mirror. Propanal is an aldehyde and has no C=C bond for bromine addition.

Question 36Organic chemistry and macromolecules

A peptide bond forms when:

  1. An amine group and a carboxyl group condense with loss of water Correct answer.
  2. Two alkene groups add bromine
  3. A ketone is reduced to an alcohol
  4. Two benzene rings form an ionic lattice

Explanation

Peptide bonds are amide links formed by condensation between an amino group and a carboxyl group, releasing water.

Question 37Organic chemistry and macromolecules

Lactic acid, CH3-CH(OH)-COOH, has how many chiral carbon atoms?

  1. 0
  2. 1 Correct answer.
  3. 2
  4. 3

Explanation

The middle carbon is attached to CH3, H, OH, and COOH, four different groups. The carboxyl carbon is planar and not chiral.

Question 38Organic chemistry and macromolecules

A polymer with many ester linkages is generally more chemically degradable than polyethene because ester linkages:

  1. Can be hydrolyzed under suitable acidic or basic conditions Correct answer.
  2. Are stronger than all C-C bonds in any condition
  3. Contain free electrons that conduct electricity
  4. Prevent any reaction with water

Explanation

Ester bonds can undergo hydrolysis, breaking the polymer chain. Polyethene has a largely nonpolar C-C backbone that is much less susceptible to hydrolysis.

Question 39Physical chemistry, amounts and reactions

What is the main effect of a catalyst on a reversible reaction?

  1. It changes the equilibrium constant
  2. It lowers the activation energy for both directions Correct answer.
  3. It makes the reaction enthalpy more negative
  4. It forces the reaction to completion

Explanation

A catalyst provides an alternative pathway with lower activation energy for forward and reverse reactions. It speeds equilibrium attainment but does not change K.

Question 40Physical chemistry, amounts and reactions

For the exothermic equilibrium N2(g) + 3H2(g) <-> 2NH3(g), which change favors ammonia formation?

  1. Increasing temperature
  2. Decreasing pressure
  3. Removing ammonia as it forms Correct answer.
  4. Adding a catalyst only

Explanation

Removing NH3 lowers product concentration, so the equilibrium shifts right to replace it. This increases ammonia yield according to Le Chatelier's principle.

Question 41Physical chemistry, amounts and reactions

In the equilibrium 2SO2(g) + O2(g) <-> 2SO3(g), increasing pressure favors the side with:

  1. More gas particles, the reactants
  2. Fewer gas particles, the products Correct answer.
  3. The larger molar masses, always the reactants
  4. The higher activation energy, always the products

Explanation

The reactant side has three moles of gas, while the product side has two. Higher pressure favors the side with fewer gas particles.

Question 42Physical chemistry, amounts and reactions

For the equilibrium H2(g) + I2(g) <-> 2HI(g), which expression is Kc?

  1. [H2][I2]/[HI]^2
  2. [HI]^2/([H2][I2]) Correct answer.
  3. 2[HI]/([H2]+[I2])
  4. [H2]+[I2]+[HI]

Explanation

Kc is products over reactants, with each concentration raised to its stoichiometric coefficient: Kc = [HI]^2 divided by [H2][I2].

Question 43Physical chemistry, amounts and reactions

Mixing aqueous silver nitrate and sodium chloride gives a white precipitate because:

  1. NaNO3 is insoluble in water
  2. AgCl is sparingly soluble Correct answer.
  3. Silver metal is formed by reduction
  4. Chloride ions become gaseous chlorine

Explanation

Ag+ and Cl- ions combine to form AgCl(s), a sparingly soluble ionic compound that appears as a white precipitate.

Question 44Physical chemistry, amounts and reactions

If the reaction quotient Q is greater than K for a reversible reaction, the system will initially shift:

  1. Toward products
  2. Toward reactants Correct answer.
  3. Nowhere, because Q greater than K means equilibrium
  4. Toward the side with more solids

Explanation

Q greater than K means there are too many products relative to equilibrium, so the reaction shifts left toward reactants until Q decreases to K.

Question 45Physical chemistry, amounts and reactions

In an industrial equilibrium process, continuously removing product usually:

  1. Shifts equilibrium toward more product Correct answer.
  2. Stops all forward reaction
  3. Changes K at constant temperature
  4. Increases activation energy

Explanation

Removing product reduces its concentration, so the system shifts toward the product side to oppose the change. K itself remains fixed at constant temperature.

Question 46Physical chemistry, amounts and reactions

For an exothermic forward reaction, increasing temperature generally causes K to:

  1. Increase, because products are favored
  2. Decrease, because reactants are favored Correct answer.
  3. Remain unchanged for all equilibria
  4. Become exactly 1

Explanation

Heat can be treated as a product for an exothermic forward reaction. Raising temperature shifts equilibrium toward reactants, so K decreases.

Question 47Physical chemistry, amounts and reactions

A rate doubles when [A] is doubled and quadruples when [B] is doubled. Which rate law fits these observations?

  1. rate = k[A][B]^2 Correct answer.
  2. rate = k[A]^2[B]
  3. rate = k[A][B]
  4. rate = k[A]^2[B]^2

Explanation

Doubling [A] doubles rate, so the reaction is first order in A. Doubling [B] quadruples rate, so it is second order in B.

Question 48Physical chemistry, amounts and reactions

A first-order reaction has a half-life of 20 minutes. How much reactant remains after 40 minutes?

  1. 75%
  2. 50%
  3. 25% Correct answer.
  4. 10%

Explanation

Forty minutes is two half-lives. After one half-life 50% remains; after two half-lives 25% remains.

Question 49Physical chemistry, amounts and reactions

On an energy profile diagram, adding a catalyst is shown by:

  1. Lowering the activation-energy peak Correct answer.
  2. Lowering only the reactant energy
  3. Raising the product energy
  4. Making products and reactants equal in energy

Explanation

A catalyst provides an alternative pathway with a lower activation energy. The energies of reactants and products, and therefore delta H, are unchanged.

Question 50Physical chemistry, amounts and reactions

For N2O4(g) <-> 2NO2(g), Kc = 0.36. Starting with 1.00 mol/L N2O4 and no NO2, what is the approximate equilibrium [NO2]?

  1. 0.26 mol/L
  2. 0.36 mol/L
  3. 0.52 mol/L Correct answer.
  4. 0.72 mol/L

Explanation

Let x mol/L N2O4 dissociate. Then [NO2] = 2x and [N2O4] = 1 - x. Kc = 4x^2/(1 - x) = 0.36, giving x about 0.258 and [NO2] about 0.52 mol/L.