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General Chemistry — GK Questions with Answers

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36 questions
  1. Which state of matter is mainly found in the Sun and stars?
    1. Solid
    2. Plasma
    3. Bose–Einstein condensate
    4. Liquid
    Show answer

    Answer: (B) Plasma

    At very high temperature gas atoms are ionised into plasma — the Sun and stars are in this state.

  2. What is needed to form a Bose–Einstein condensate?
    1. Very high temperature
    2. A strong electric field
    3. Very high pressure
    4. Temperature very close to absolute zero
    Show answer

    Answer: (D) Temperature very close to absolute zero

    A very low-density gas cooled to nano-kelvin temperatures puts its atoms into one quantum state.

  3. Which of these sublimes?
    1. Naphthalene
    2. Sugar
    3. Salt
    4. Sand
    Show answer

    Answer: (A) Naphthalene

    Naphthalene, camphor, ammonium chloride and iodine turn straight into vapour on heating without melting.

  4. The rate of evaporation decreases when —
    1. temperature rises
    2. wind becomes faster
    3. humidity of air rises
    4. surface area increases
    Show answer

    Answer: (C) humidity of air rises

    Humid air already has much water vapour, so less new vapour can form — clothes dry slowly in the rains.

  5. Why does food take longer to cook on mountains?
    1. There is less oxygen
    2. It is colder
    3. Lower air pressure makes water boil below 100 °C
    4. Water is heavier
    Show answer

    Answer: (C) Lower air pressure makes water boil below 100 °C

    Lower pressure lowers the boiling point; food cooks slowly in water boiling at a lower temperature.

  6. If the pressure of a gas is doubled at constant temperature, its volume becomes —
    1. half
    2. double
    3. four times
    4. the same
    Show answer

    Answer: (A) half

    By Boyle’s law PV is constant; if P doubles, V halves.

  7. 300 mL of gas at 27 °C is heated to 127 °C at constant pressure. New volume?
    1. 600 mL
    2. 1411 mL
    3. 225 mL
    4. 400 mL
    Show answer

    Answer: (D) 400 mL

    Temperature in kelvin for Charles’s law: V₂ = 300 × 400/300 = 400 mL.

  8. At the same temperature and pressure, which gas diffuses fastest?
    1. CO₂
    2. H₂
    3. N₂
    4. O₂
    Show answer

    Answer: (B) H₂

    By Graham’s law the rate of diffusion is inversely proportional to √M; H₂ (M = 2) is lightest, so fastest.

  9. When do real gases behave like an ideal gas?
    1. Low pressure, high temperature
    2. High pressure, low temperature
    3. High pressure, high temperature
    4. Low pressure, low temperature
    Show answer

    Answer: (A) Low pressure, high temperature

    At low pressure molecules are far apart (own volume negligible) and at high temperature they are fast (attraction negligible).

  10. How many atoms are there in a face-centred cubic (fcc) unit cell?
    1. 1
    2. 2
    3. 4
    4. 6
    Show answer

    Answer: (C) 4

    8 corners × 1/8 + 6 faces × 1/2 = 1 + 3 = 4.

  1. In which crystal defect does the density of the solid decrease?
    1. Frenkel
    2. Schottky
    3. Both
    4. Neither
    Show answer

    Answer: (B) Schottky

    In a Schottky defect both cations and anions are missing from the crystal, so density falls; in Frenkel an ion only changes place.

  2. Which of these is a mixture?
    1. Water
    2. Carbon dioxide
    3. Table salt
    4. Brass
    Show answer

    Answer: (D) Brass

    Brass is an alloy of copper and zinc — a homogeneous mixture whose composition can vary.

  3. Which of these is a chemical change?
    1. Melting of ice
    2. Dissolving of salt
    3. Tearing of paper
    4. Milk turning into curd
    Show answer

    Answer: (D) Milk turning into curd

    In making curd bacteria turn the lactose of milk into lactic acid — a new substance forms.

  4. Best method to separate a mixture of salt and ammonium chloride?
    1. Filtration
    2. Sublimation
    3. Distillation
    4. Centrifugation
    Show answer

    Answer: (B) Sublimation

    NH₄Cl sublimes on heating and deposits on a cold surface, leaving the salt behind.

  5. By which method is crude petroleum separated into petrol, diesel etc.?
    1. Simple distillation
    2. Steam distillation
    3. Fractional distillation
    4. Chromatography
    Show answer

    Answer: (C) Fractional distillation

    The parts have boiling points very close together, so fractional distillation with a fractionating column is needed.

  6. Method to separate the colours mixed in black ink?
    1. Chromatography
    2. Evaporation
    3. Crystallisation
    4. Sublimation
    Show answer

    Answer: (A) Chromatography

    Different colours rise to different heights on paper (difference in adsorption) — this is paper chromatography.

  7. The mass ratio of hydrogen to oxygen in water is always 1 : 8 — this illustrates which law?
    1. Conservation of mass
    2. Definite proportions
    3. Multiple proportions
    4. Gaseous volumes
    Show answer

    Answer: (B) Definite proportions

    Proust’s law of definite proportions — a compound always has its elements in the same ratio by mass.

  8. Number of molecules in 18 g of water?
    1. 18 × 10²³
    2. 3.011 × 10²³
    3. 1.807 × 10²⁴
    4. 6.022 × 10²³
    Show answer

    Answer: (D) 6.022 × 10²³

    18 g = 1 mole of water = 6.022 × 10²³ molecules (atoms are three times this).

  9. Mass of 44.8 L of CO₂ at STP?
    1. 88 g
    2. 22 g
    3. 44 g
    4. 176 g
    Show answer

    Answer: (A) 88 g

    44.8/22.4 = 2 moles; 2 × 44 = 88 g.

  10. A compound has empirical formula CH₂O and molar mass 180. Molecular formula?
    1. C₂H₄O₂
    2. C₃H₆O₃
    3. C₆H₁₂O₆
    4. C₅H₁₀O₅
    Show answer

    Answer: (C) C₆H₁₂O₆

    n = 180/30 = 6, so C₆H₁₂O₆ (glucose).

  1. In making water from 4 g H₂ and 48 g O₂, which is the limiting reagent?
    1. O₂
    2. Both equal
    3. H₂
    4. Neither
    Show answer

    Answer: (C) H₂

    2 moles of H₂ need 1 mole of O₂ but 1.5 moles are present — H₂ runs out first; 36 g of water forms.

  2. 4 g NaOH is used to make 500 mL of solution. Molarity?
    1. 0.2 M
    2. 0.1 M
    3. 0.4 M
    4. 2 M
    Show answer

    Answer: (A) 0.2 M

    n = 4/40 = 0.1 mole; M = 0.1/0.5 = 0.2 M.

  3. Which term of concentration does not change with temperature?
    1. Molarity
    2. Normality
    3. w/v percent
    4. Molality
    Show answer

    Answer: (D) Molality

    Molality uses the mass of solvent, not volume; mass does not change with temperature.

  4. As temperature rises, the solubility of gases in water —
    1. increases
    2. decreases
    3. stays the same
    4. first rises then falls
    Show answer

    Answer: (B) decreases

    Dissolving a gas is exothermic; on heating the gas escapes — ponds lose oxygen in summer.

  5. Bubbles rushing out on opening a soda bottle are explained by which law?
    1. Henry
    2. Raoult
    3. Boyle
    4. Graham
    Show answer

    Answer: (A) Henry

    By Henry’s law the solubility of a gas is proportional to pressure; when the cap opens the pressure falls and CO₂ escapes.

  6. Among 0.1 m solutions, which has the lowest freezing point?
    1. Glucose
    2. Urea
    3. CaCl₂
    4. NaCl
    Show answer

    Answer: (C) CaCl₂

    CaCl₂ gives three ions (i = 3), so its freezing point depression is the largest.

  7. Why is ethylene glycol added to car radiators in cold countries?
    1. To lower the boiling point
    2. To lower the freezing point
    3. To lubricate the engine
    4. To stop rust
    Show answer

    Answer: (B) To lower the freezing point

    This uses a colligative property (freezing point depression) — water does not freeze and damage the engine.

  8. When a red blood cell is put in a hypotonic solution, it —
    1. shrinks
    2. freezes
    3. shows no effect
    4. swells and may burst
    Show answer

    Answer: (D) swells and may burst

    The outside is less concentrated, so water enters the cell by osmosis — haemolysis.

  9. In which is the Tyndall effect seen?
    1. Sugar solution
    2. Salt solution
    3. Distilled water
    4. Starch solution
    Show answer

    Answer: (D) Starch solution

    Starch solution is colloidal and its particles scatter light; true solutions do not show this effect.

  10. Jelly is which type of colloid?
    1. Sol
    2. Gel
    3. Aerosol
    4. Foam
    Show answer

    Answer: (B) Gel

    In jelly a liquid (water) is trapped in a solid network — a liquid-in-solid colloid is called a gel.

  1. Why does a delta form at a river mouth?
    1. Evaporation
    2. Tides
    3. Coagulation of colloidal clay by salty water
    4. Wind
    Show answer

    Answer: (C) Coagulation of colloidal clay by salty water

    Ions in sea water remove the charge on the colloidal clay particles and they settle.

  2. A reaction has negative ΔH and positive ΔS. It is —
    1. spontaneous at all temperatures
    2. spontaneous only at low temperature
    3. spontaneous only at high temperature
    4. never spontaneous
    Show answer

    Answer: (A) spontaneous at all temperatures

    ΔG = ΔH − TΔS — both terms make ΔG negative, so it is spontaneous at all temperatures.

  3. In N₂ + 3H₂ ⇌ 2NH₃ (exothermic), the yield of ammonia increases on —
    1. lowering pressure
    2. raising pressure
    3. raising temperature
    4. adding more catalyst
    Show answer

    Answer: (B) raising pressure

    Raising pressure shifts the equilibrium to fewer gaseous moles (2); a catalyst only increases the rate, not the yield.

  4. pH of a 0.001 M NaOH solution?
    1. 3
    2. 13
    3. 7
    4. 11
    Show answer

    Answer: (D) 11

    [OH⁻] = 10⁻³ → pOH = 3 → pH = 14 − 3 = 11.

  5. A first-order reaction has a half-life of 10 minutes. How much reactant is left after 30 minutes?
    1. 12.5%
    2. 25%
    3. 50%
    4. 33%
    Show answer

    Answer: (A) 12.5%

    30 minutes = 3 half-lives; (½)³ = 1/8 = 12.5%.

  6. How much copper (63.5) is deposited when 1930 C passes through CuSO₄ solution?
    1. 6.35 g
    2. 1.27 g
    3. 0.635 g
    4. 0.3175 g
    Show answer

    Answer: (C) 0.635 g

    1930 C = 0.02 F; Cu²⁺ needs 2 electrons → 0.01 mole = 0.635 g.

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