Chemistry SPSC-Practice-4

Prepare for SPSC Chemistry examinations with 40 fresh MCQs covering atomic structure, chemical calculations, equilibrium, thermodynamics, electrochemistry, inorganic chemistry, organic chemistry and analytical techniques. Practise with verified answers and explanations.

Practice questions

What is the approximate value of Avogadro's constant?
- 6.022 × 10²³ mol⁻¹
- 3.011 × 10²³ mol⁻¹
- 9.109 × 10⁻³¹ mol⁻¹
- 1.602 × 10⁻¹⁹ mol⁻¹
Isotopes of the same element have:
- Different numbers of protons
- The same number of protons but different numbers of neutrons
- The same mass number
- Different atomic numbers
Which quantum number specifies the main energy level of an electron?
- Principal quantum number
- Azimuthal quantum number
- Magnetic quantum number
- Spin quantum number
According to the Pauli exclusion principle, an atomic orbital can contain a maximum of:
- One electron
- Two electrons with opposite spins
- Three electrons
- Four electrons
Across a period from left to right, the effective nuclear charge generally:
- Decreases
- Remains constant
- Increases
- Becomes zero
How many electrons can the third principal energy shell hold at its maximum theoretical capacity?
- 8
- 18
- 32
- 50
What is the molarity of a solution containing 0.5 moles of solute in 2 litres of solution?
- 0.25 M
- 0.50 M
- 1.00 M
- 2.50 M
What is the empirical formula of glucose, whose molecular formula is C₆H₁₂O₆?
- CHO
- CH₂O
- C₂H₄O₂
- C₆H₁₂O₆
How many moles are present in 44 grams of carbon dioxide (CO₂)? (Molar mass = 44 g/mol)
- 0.5 mol
- 1 mol
- 2 mol
- 4 mol
At constant pressure, the volume of a fixed amount of an ideal gas is directly proportional to its:
- Absolute temperature
- Molar mass
- Density
- Molecular mass
Which instrument is commonly used to measure atmospheric pressure?
- Hygrometer
- Barometer
- Calorimeter
- Manometer
At 25°C, a neutral aqueous solution has a pH of:
- 1
- 5
- 7
- 14
A buffer solution is one that:
- Prevents all chemical reactions
- Resists significant changes in pH when small amounts of acid or base are added
- Always has a pH of 7
- Contains only a strong acid
For the reaction N₂ + 3H₂ ⇌ 2NH₃, which expression represents Kc?
- [NH₃]² / ([N₂][H₂]³)
- [N₂][H₂]³ / [NH₃]²
- [NH₃] / ([N₂][H₂])
- [N₂]²[H₂] / [NH₃]
For an exothermic reaction, the enthalpy change (ΔH) is:
- Positive
- Negative
- Always zero
- Undefined
A catalyst increases the rate of a chemical reaction mainly by:
- Increasing the activation energy
- Providing an alternative pathway with lower activation energy
- Increasing the mass of the reactants
- Changing the equilibrium constant
Which statement about the half-life of a first-order reaction is correct?
- It depends directly on initial concentration
- It is independent of initial concentration
- It is always zero
- It increases with the amount of catalyst
Which term describes the minimum energy required for a chemical reaction to occur?
- Ionisation energy
- Activation energy
- Lattice energy
- Hydration energy
Which electrode is the site of reduction in an electrochemical cell?
- Anode
- Cathode
- Salt bridge
- Electrolyte surface only
What is the standard electrode potential of the standard hydrogen electrode?
- +1.00 V
- −1.00 V
- 0.00 V
- +0.50 V
During electrolysis of concentrated aqueous sodium chloride, which gas is generally produced at the anode?
- Hydrogen
- Chlorine
- Nitrogen
- Carbon dioxide
The reddish-brown substance commonly called rust is mainly:
- Iron sulphide
- Hydrated iron(III) oxide
- Iron carbonate
- Iron chloride
Which ions are mainly responsible for the hardness of natural water?
- Sodium and potassium
- Calcium and magnesium
- Chloride and nitrate
- Hydrogen and hydroxide
Temporary hardness of water can be removed by:
- Boiling
- Freezing
- Adding common salt
- Passing air through it
Which catalyst is commonly used in the industrial Haber process?
- Iron
- Nickel
- Platinum
- Copper
Which catalyst is commonly used in the Contact process for manufacturing sulphuric acid?
- Vanadium(V) oxide
- Iron
- Nickel
- Zinc oxide
Which oxide is amphoteric?
- Na₂O
- SO₃
- Al₂O₃
- CO₂
Which colour is produced in a flame test by sodium compounds?
- Lilac
- Brick red
- Golden yellow
- Apple green
Which element belongs to Group 18 of the periodic table?
- Chlorine
- Argon
- Sulphur
- Sodium
What is the oxidation state of sulphur in H₂SO₄?
- +2
- +4
- +6
- −2
Which functional group is characteristic of an ester?
- –COO–
- –OH
- –CHO
- –NH₂
Which gas is released when a carboxylic acid reacts with sodium bicarbonate?
- Hydrogen
- Carbon dioxide
- Oxygen
- Nitrogen
Which monomer is used to manufacture polyethene?
- Ethene
- Ethyne
- Benzene
- Methane
Which bond links amino acids together in proteins?
- Glycosidic bond
- Peptide bond
- Phosphodiester bond
- Hydrogen bond
Which sugar is a component of RNA?
- Deoxyribose
- Ribose
- Fructose
- Galactose
In paper chromatography, the substance that moves with the solvent is called the:
- Stationary phase
- Mobile phase
- Adsorbent only
- Precipitate
What colour does phenolphthalein produce in an alkaline solution?
- Red
- Pink
- Yellow
- Blue
Which analytical technique is commonly used to determine the mass-to-charge ratio of ions?
- Mass spectrometry
- Titration
- Filtration
- Calorimetry
Which method is commonly used to separate two miscible liquids with sufficiently different boiling points?
- Simple distillation
- Filtration
- Sublimation
- Decantation
Which law states that the total pressure of a mixture of non-reacting gases equals the sum of their partial pressures?
- Boyle's law
- Charles's law
- Dalton's law of partial pressures
- Graham's law