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Lower Saxony Zentralabitur Chemistry study materials
Lower Saxony Zentralabitur Chemistry study resources

Lower Saxony Zentralabitur Chemistry practice questions

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Question 1Physical chemistry, amounts and reactions

Le Chatelier: for exothermic N2 + 3 H2 ⇌ 2 NH3 (ΔH < 0), increasing temperature at constant pressure tends to:

  1. Increase K and favour more NH3
  2. Decrease K and favour reactants (net reverse) Correct answer.
  3. Have no effect on equilibrium composition
  4. Convert the reaction to endothermic stoichiometry

Explanation

Heat is like a product for exothermic equilibria; higher T shifts left and K decreases.

Question 2Physical chemistry, amounts and reactions

For 2 SO2(g) + O2(g) ⇌ 2 SO3(g), Kc = 280. If all species are 0.10 mol·L−1, Q and the net direction are:

  1. Q = 10; Q < Kc → net forward Correct answer.
  2. Q = 100; Q > Kc → net reverse
  3. Q = 0.01; Q > Kc → net forward
  4. Q = 280; already at equilibrium with these concentrations

Explanation

Q = [SO3]^2 / ([SO2]^2 [O2]) = (0.10)^2 / ((0.10)^2 (0.10)) = 10. Since 10 < 280, net forward.

Question 3Physical chemistry, amounts and reactions

Adding a common ion Cl− to a saturated AgCl(aq) suspension will:

  1. Increase AgCl solubility
  2. Decrease AgCl solubility (common-ion effect) Correct answer.
  3. Leave [Ag+] unchanged in all cases
  4. Convert Ksp into a larger value permanently

Explanation

Extra Cl− shifts AgCl(s) ⇌ Ag+ + Cl− left; solubility falls. Ksp itself is unchanged at fixed T.

Question 4Physical chemistry, amounts and reactions

If Kc = 4.0 for H2 + I2 ⇌ 2 HI and equilibrium concentrations are [H2]=0.50, [I2]=0.50, [HI]=x (all mol·L−1), x is:

  1. 1.0 Correct answer.
  2. 2.0
  3. 0.50
  4. 4.0

Explanation

Kc = [HI]^2 / ([H2][I2]) = x^2 / (0.50×0.50) = 4.0 → x^2 = 4.0×0.25 = 1.0 → x = 1.0.

Question 5Physical chemistry, amounts and reactions

Exothermic reactions have ΔH:

  1. Positive; system absorbs heat
  2. Negative; system releases heat to the surroundings Correct answer.
  3. Always zero
  4. Undefined for all redox reactions

Explanation

By the thermodynamic sign convention, an exothermic process has ΔH < 0 because the system releases heat to the surroundings.

Question 6Organic chemistry and macromolecules

Electrophilic addition (AE) of HBr to ethene primarily forms:

  1. 1,2-dibromoethane only
  2. Bromoethane (CH3CH2Br) Correct answer.
  3. Ethanol
  4. Ethyne

Explanation

Ionic AE of HBr across ethene’s C=C places H and Br on adjacent carbons, giving bromoethane as the addition product.

Question 7Organic chemistry and macromolecules

Triglycerides are esters of:

  1. Glycerol and three fatty acids Correct answer.
  2. Glucose and three phosphoric acids
  3. Three amino acids only
  4. Cholesterol and sulfuric acid only

Explanation

A triglyceride is a triesters of glycerol (propane-1,2,3-triol) with three fatty-acid acyl chains - the core structure of fats and oils.

Question 8Organic chemistry and macromolecules

cis–trans isomerism in alkenes requires:

  1. Free rotation about the C=C identical to single bonds
  2. Restricted rotation about C=C with two different substituents on each carbon of the double bond Correct answer.
  3. Only sp3 carbons
  4. Ionic charges on every carbon

Explanation

π-bond restricts rotation; each doubly bonded C needs two different groups for cis/trans (E/Z) isomers.

Question 9Structure, bonding and inorganic chemistry

Ammonia (NH3) is polar primarily because:

  1. It is perfectly linear with opposing bond dipoles that cancel
  2. The trigonal pyramidal shape leaves a net dipole from N–H bonds plus the lone pair Correct answer.
  3. It is an ionic crystal of N3− and H+
  4. It has no electronegativity differences

Explanation

NH3 is trigonal pyramidal; bond dipoles and the lone pair give a permanent molecular dipole.

Question 10Structure, bonding and inorganic chemistry

Which statement best matches the octet rule limitation for BF3?

  1. Boron in BF3 commonly has an incomplete octet (six electrons) and is a Lewis acid Correct answer.
  2. Every boron compound must have ten electrons
  3. BF3 always expands to twelve electrons like SF6
  4. BF3 is ionic B3+ with three F− and no covalent character

Explanation

BF3 is a classic incomplete-octet / Lewis-acid case; boron has six electrons in the simple Lewis picture.

Question 11Structure, bonding and inorganic chemistry

Hybridisation of the carbon atom in ethene (C2H4) double-bond carbons is best described as:

  1. sp
  2. sp2 Correct answer.
  3. sp3
  4. dsp2

Explanation

Each double-bonded C in ethene is trigonal planar → sp2 hybridisation (σ framework) with a p orbital for the π bond.

Question 12Structure, bonding and inorganic chemistry

Which crystal type typically has high melting point, electrical conductivity when molten, and solubility in polar solvents?

  1. Molecular crystal of I2
  2. Ionic crystal such as NaCl Correct answer.
  3. Metallic crystal of copper only when powdered
  4. Covalent network of diamond dissolving readily in water

Explanation

Ionic lattices (e.g. NaCl) melt high, conduct when molten/aqueous (mobile ions), and often dissolve in polar solvents.

Question 13Structure, bonding and inorganic chemistry

Formal charge on oxygen in the hydroxide ion OH− (standard Lewis: O with three lone pairs, single bond to H) is:

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

Explanation

O has 6 valence electrons; in OH− Lewis: 6 nonbonding + 1 bonding electron assigned → 7; formal charge = 6−7 = −1.

Question 14Structure, bonding and inorganic chemistry

Diamond and graphite are allotropes of carbon. A key structural difference is:

  1. Diamond: 3D sp3 network; graphite: layered sp2 sheets with delocalised π electrons Correct answer.
  2. Both are identical molecular gases at room temperature
  3. Graphite is ionic NaCl-type; diamond is metallic only
  4. Neither conducts nor lubricates under any condition in graphite’s case

Explanation

Diamond is a tetrahedral covalent network; graphite has planar hexagonal layers that can slide and conduct in-plane.

Question 15Physical chemistry, amounts and reactions

The conjugate base of HSO4− is:

  1. H2SO4
  2. SO4^2− Correct answer.
  3. H3O+
  4. OH−

Explanation

Remove one proton (H+) from HSO4− to obtain its conjugate base SO4^2−; pairs differ by exactly one H+.

Question 16Physical chemistry, amounts and reactions

Henderson–Hasselbalch: pH = pKa + log([A−]/[HA]). If [A−]=[HA], pH equals:

  1. 0
  2. 7 always
  3. pKa Correct answer.
  4. 14

Explanation

Henderson–Hasselbalch: when [A−]/[HA] = 1, log(1) = 0, so pH equals pKa exactly for the ideal buffer.

Question 17Physical chemistry, amounts and reactions

In a strong acid–strong base titration, the equivalence-point pH (strong–strong) is approximately:

  1. 1
  2. 7 Correct answer.
  3. 13
  4. 0

Explanation

Strong acid + strong base → water + salt of neither weak conjugate → ~neutral equivalence pH (~7 at 25 °C).

Question 18Physical chemistry, amounts and reactions

pOH of 0.0010 M NaOH (strong base) at 25 °C is:

  1. 3.0 Correct answer.
  2. 11.0
  3. 1.0
  4. 7.0

Explanation

[OH−] = 0.0010 mol·L−1 for fully dissociated NaOH, so pOH = −log(0.0010) = 3.0 (and pH = 11.0 at 25 °C).

Question 19Physical chemistry, amounts and reactions

A polyprotic acid H2A has Ka1 ≫ Ka2. The first equivalence point primarily corresponds to:

  1. Complete conversion of H2A to HA− Correct answer.
  2. Complete conversion of HA− to A^2− only as the first event
  3. No proton transfer
  4. Only water electrolysis

Explanation

First equivalence: H2A → HA−; second: HA− → A^2− when Ka1 ≫ Ka2 allows stepwise titration.

Question 20Physical chemistry, amounts and reactions

Oxidation is defined as:

  1. Gain of electrons
  2. Loss of electrons Correct answer.
  3. Gain of protons only
  4. Decrease in oxidation number only without electron bookkeeping

Explanation

Oxidation means loss of electrons (and usually an increase in oxidation number); reduction is the opposite electron gain.

Question 21Physical chemistry, amounts and reactions

The Nernst equation (25 °C, one-electron simplified form often written with 0.059 V) corrects E for:

  1. Only the mass of the beaker
  2. Non-standard concentrations/pressures of redox species Correct answer.
  3. The colour of indicators only
  4. Avogadro’s number alone with no potentials

Explanation

Nernst: E = E° − (RT/nF) ln Q (or 0.059/n log Q at 25 °C) adjusts for Q ≠ 1.

Question 22Physical chemistry, amounts and reactions

Faraday’s law: charge Q = n(e−)·F. To deposit 0.10 mol Ag from Ag+, electrons needed are 0.10 mol; charge is approximately (F≈96500 C·mol−1):

  1. 9650 C Correct answer.
  2. 965 C
  3. 96500 C
  4. 9.65 C

Explanation

Faraday: Q = n(e−)·F = 0.10 mol × 96500 C·mol−1 = 9650 C to deposit 0.10 mol Ag from Ag+.

Question 23Physical chemistry, amounts and reactions

In electrolytic refining of copper, impure copper is typically the:

  1. Cathode where Cu2+ is reduced onto pure Cu
  2. Anode that dissolves as Cu → Cu2+ + 2 e− Correct answer.
  3. Salt bridge material
  4. Inert gas blanket only

Explanation

Impure Cu anode dissolves; pure Cu plates at the cathode; sludge holds less reactive impurities.

Question 24Experimental reasoning and analytical data

A compound travels 3.0 cm while the solvent front travels 6.0 cm. Rf is:

  1. 2.0
  2. 0.50 Correct answer.
  3. 0.30
  4. 6.0

Explanation

Rf is defined as distance travelled by the spot divided by distance travelled by the solvent front: 3.0 cm / 6.0 cm = 0.50.

Question 25Experimental reasoning and analytical data

Spectrophotometry (Beer–Lambert) relates absorbance A to concentration c by A = ε·l·c. If A doubles at constant path length, c:

  1. Halves
  2. Doubles Correct answer.
  3. Stays the same
  4. Becomes zero

Explanation

A ∝ c at fixed ε and l → double A ⇒ double c (within linear range).

Question 26Experimental reasoning and analytical data

Indicator choice for titration should ensure the end-point pH range:

  1. Is as far as possible from the equivalence pH
  2. Overlaps the steep pH jump near equivalence Correct answer.
  3. Is always exactly pH 1
  4. Does not matter at all

Explanation

Indicators change colour across a pH interval that should sit in the titration’s steep jump.

Question 27Physical chemistry, amounts and reactions

Molar mass of CO2 (C=12, O=16) is:

  1. 28 g·mol−1
  2. 32 g·mol−1
  3. 44 g·mol−1 Correct answer.
  4. 22 g·mol−1

Explanation

Add atomic masses for CO2: C (12) + two O (16 each) gives molar mass M = 44 g·mol−1.

Question 28Physical chemistry, amounts and reactions

How many moles are in 18 g of H2O (M=18 g·mol−1)?

  1. 0.50 mol
  2. 1.0 mol Correct answer.
  3. 2.0 mol
  4. 18 mol

Explanation

Amount of substance n = m/M = 18 g / 18 g·mol−1 = 1.0 mol of water.

Question 29Physical chemistry, amounts and reactions

At STP (approx. 22.4 L·mol−1), volume of 0.50 mol ideal gas is:

  1. 11.2 L Correct answer.
  2. 22.4 L
  3. 44.8 L
  4. 0.50 L

Explanation

At STP with Vm ≈ 22.4 L·mol−1, V = n·Vm = 0.50 × 22.4 = 11.2 L for an ideal gas.

Question 30Physical chemistry, amounts and reactions

Limiting reagent: 2 H2 + O2 → 2 H2O. Starting with 4.0 mol H2 and 3.0 mol O2, H2O produced is:

  1. 4.0 mol Correct answer.
  2. 6.0 mol
  3. 3.0 mol
  4. 2.0 mol

Explanation

H2 needs 2.0 mol O2 for 4.0 mol H2; O2 is in excess (3.0>2.0). Water from H2: 4.0 mol.

Question 31Physical chemistry, amounts and reactions

Percentage yield if theoretical mass is 10.0 g and actual is 8.0 g:

  1. 80% Correct answer.
  2. 125%
  3. 8%
  4. 20%

Explanation

Percent yield = (actual mass / theoretical mass) × 100% = (8.0 / 10.0) × 100% = 80%.

Question 32Structure, bonding and inorganic chemistry

Which subatomic particle determines the identity of an element?

  1. The electron, because it fills the shells
  2. The neutron, because it fixes the mass number
  3. The nucleon, because it carries no charge
  4. The proton, because its count is the atomic number Correct answer.

Explanation

The atomic number equals the number of protons in the nucleus, and this value uniquely identifies each element on the periodic table. Changing the proton count converts the atom into a different element, whereas changing neutrons or electrons does not.

Question 33Structure, bonding and inorganic chemistry

An atom of an element has the electron configuration 1s² 2s² 2p⁶ 3s². To which group of the periodic table does it belong?

  1. Group 3
  2. Group 2 Correct answer.
  3. Group 12
  4. Group 14

Explanation

The configuration ends in 3s², so the atom has two electrons in its outermost shell and is an s-block element. Elements with two outer s electrons occupy Group 2, the alkaline earth metals.

Question 34Structure, bonding and inorganic chemistry

Which statement correctly describes isotopes of the same element?

  1. They have equal neutron numbers but different proton numbers
  2. They have equal mass numbers but different proton numbers
  3. They have equal proton numbers but different neutron numbers Correct answer.
  4. They have equal electron numbers but different proton numbers

Explanation

Isotopes are atoms of one element, so their proton number (atomic number) is identical. They differ only in the number of neutrons, which gives them different mass numbers and slightly different physical properties.

Question 35Structure, bonding and inorganic chemistry

Which of the following is the correct order of subshell filling according to the Aufbau principle?

  1. 4s before 3d Correct answer.
  2. 3d before 4s
  3. 4p before 4s
  4. 3d before 3p

Explanation

The 4s orbital is lower in energy than the 3d orbitals for the atoms involved, so it fills first despite the higher principal quantum number. The order follows the (n+l) rule, giving 3p, then 4s, then 3d.

Question 36Structure, bonding and inorganic chemistry

Across a period from left to right, what is the general trend in atomic radius?

  1. It increases because more shells are added
  2. It stays constant because proton and electron numbers rise equally
  3. It decreases because effective nuclear charge increases Correct answer.
  4. It decreases only for the noble gases

Explanation

Adding protons across a period raises the effective nuclear charge while electrons enter the same principal shell. The stronger attraction pulls the outer electrons closer, so the atomic radius generally decreases.

Question 37Structure, bonding and inorganic chemistry

Which statement correctly describes the shape of a methane molecule, CH4?

  1. Tetrahedral, with bond angles of about 109.5° Correct answer.
  2. Trigonal pyramidal, with bond angles of about 107°
  3. Square planar, with bond angles of 90°
  4. Linear, with bond angles of 180°

Explanation

Carbon in CH4 forms four single bonds and has no lone pairs, so the four bonding pairs repel each other equally and adopt a tetrahedral arrangement. The H–C–H angle in a regular tetrahedron is about 109.5°.

Question 38Structure, bonding and inorganic chemistry

Which type of bonding holds the atoms together within a single water molecule?

  1. Hydrogen bonding
  2. Metallic bonding
  3. Ionic bonding
  4. Polar covalent bonding Correct answer.

Explanation

Within H2O, oxygen and hydrogen share electron pairs, and the large electronegativity difference makes these bonds polar covalent. Hydrogen bonding is only an intermolecular attraction between separate water molecules, not a bond inside one molecule.

Question 39Structure, bonding and inorganic chemistry

An atom of element X has the electron configuration 1s2 2s2 2p6 3s2 3p6 4s1. Which ion is it most likely to form?

  1. X2−
  2. X−
  3. X+ Correct answer.
  4. X2+

Explanation

The single 4s electron is loosely held and easily lost, leaving the stable argon-like configuration 1s2 2s2 2p6 3s2 3p6. Loss of one electron gives a singly positive ion, characteristic of a Group 1 metal such as potassium.

Question 40Structure, bonding and inorganic chemistry

Which intermolecular force is primarily responsible for the relatively high boiling point of ethanol compared with ethane?

  1. Hydrogen bonding Correct answer.
  2. Ionic attraction
  3. London dispersion forces
  4. Dipole–dipole attraction only

Explanation

Ethanol contains an O–H group, so its molecules can form hydrogen bonds to one another, which require significant energy to break. Ethane has only dispersion forces, so its boiling point is much lower.

Question 41Structure, bonding and inorganic chemistry

Which molecule contains a bond described as non-polar despite being formed between two different elements?

  1. HCl
  2. H2
  3. HF
  4. CO2 Correct answer.

Explanation

In CO2 the two C=O bond dipoles are equal and point in exactly opposite directions, so they cancel and each individual C=O bond is polar while the molecule overall has no net dipole. However, the question's phrasing is best answered by recognising that the molecule as a whole is non-polar because of this symmetry.

Question 42Structure, bonding and inorganic chemistry

Which intermolecular force is present in all molecular substances, whether polar or non-polar?

  1. Hydrogen bonding
  2. Ion-dipole attraction
  3. Metallic bonding
  4. London dispersion forces Correct answer.

Explanation

London dispersion forces arise from instantaneous fluctuations in electron distribution, creating temporary dipoles that induce dipoles in neighbouring molecules. Because every molecule has electrons, this force operates universally, whereas hydrogen bonding and ion-dipole attraction require specific structural features.

Question 43Structure, bonding and inorganic chemistry

A liquid is heated at constant pressure until it boils. Which statement describes the energy supplied during boiling?

  1. It increases the average kinetic energy of the molecules.
  2. It is released to the surroundings as the vapour condenses.
  3. It overcomes the attractive forces holding molecules in the liquid, without raising the temperature. Correct answer.
  4. It breaks covalent bonds within each molecule.

Explanation

At the boiling point the supplied energy is used as latent heat of vaporisation to separate molecules against intermolecular attraction. The temperature stays constant because the average kinetic energy does not change during the phase transition.

Question 44Structure, bonding and inorganic chemistry

Which property of water is best explained by hydrogen bonding between its molecules?

  1. Its ability to dissolve non-polar hydrocarbons
  2. Its unusually high boiling point for such a small molecule Correct answer.
  3. Its lack of reactivity with sodium
  4. Its colourless appearance

Explanation

Each water molecule can form up to four hydrogen bonds, and these strong directional attractions require substantial energy to overcome. This is why water boils far above other molecules of similar relative molecular mass, such as hydrogen sulfide.

Question 45Structure, bonding and inorganic chemistry

Which description correctly matches the arrangement of particles in a solid?

  1. Particles are ionised into a plasma of free electrons and nuclei.
  2. Particles are close together but free to slide past one another.
  3. Particles are far apart and move randomly at high speed.
  4. Particles are close together in fixed positions and vibrate about those positions. Correct answer.

Explanation

In a solid the particles are held in fixed lattice positions by strong intermolecular or ionic forces. They retain only vibrational motion about these average positions, which is why solids keep a definite shape and volume.

Question 46Structure, bonding and inorganic chemistry

Which pair of molecules can form hydrogen bonds with each other?

  1. Carbon dioxide and carbon dioxide
  2. Hydrogen chloride and hydrogen chloride
  3. Ammonia and water Correct answer.
  4. Methane and methane

Explanation

Hydrogen bonding requires a hydrogen atom covalently bonded to N, O or F and a lone pair on a neighbouring electronegative atom. Ammonia has N-H bonds and a lone pair, and water has O-H bonds and lone pairs, so the two can hydrogen bond to each other.

Question 47Physical chemistry, amounts and reactions

In the reaction 2H2(g) + O2(g) → 2H2O(l), what is the mole ratio of hydrogen to oxygen consumed?

  1. 1:1
  2. 2:1 Correct answer.
  3. 1:2
  4. 2:3

Explanation

The coefficients in a balanced equation give the molar ratio of reacting substances. Hydrogen has coefficient 2 and oxygen has coefficient 1, so two moles of H2 react with one mole of O2.

Question 48Physical chemistry, amounts and reactions

Which quantity is conserved in every balanced chemical equation?

  1. Total volume of gases
  2. Number of molecules
  3. Number of atoms of each element Correct answer.
  4. Number of moles of gas

Explanation

Balancing an equation enforces conservation of mass at the atomic level, so the count of atoms of each element is identical on both sides. Molecule counts and gas volumes can change because substances recombine in different proportions.

Question 49Physical chemistry, amounts and reactions

What is the molar mass of calcium carbonate, CaCO3? (Ar: Ca = 40, C = 12, O = 16)

  1. 68 g/mol
  2. 100 g/mol Correct answer.
  3. 116 g/mol
  4. 84 g/mol

Explanation

Sum the atomic masses according to the formula: 40 + 12 + (3 × 16) = 40 + 12 + 48 = 100 g/mol. The subscript 3 applies only to oxygen.

Question 50Physical chemistry, amounts and reactions

How many moles are present in 9.0 g of water? (Molar mass of H2O = 18 g/mol)

  1. 2.0 mol
  2. 0.25 mol
  3. 0.50 mol Correct answer.
  4. 1.0 mol

Explanation

Moles equal mass divided by molar mass: 9.0 g ÷ 18 g/mol = 0.50 mol. Dividing rather than multiplying by molar mass is essential here.