CSS - PMS - CCE - PCS - General Science
Acid/Base
The pH of pure water at 25°C is approximately:
A. 0
B. 5
C. 7
D. 14
Correct Answer: C
A: Incorrect because pH 0 is strongly acidic. B: Incorrect because pH 5 is acidic. C: Correct because pure water has equal H⁺ and OH⁻ concentrations of about 1 × 10⁻⁷ M, giving pH 7. D: Incorrect because pH 14 is strongly basic on the common aqueous scale.
CSS - PMS - CCE - PCS - General Science
Acid/Base
At 25°C, a solution with pH greater than 7 is generally:
A. Acidic
B. Basic
C. Neutral
D. Pure water
Correct Answer: B
A: Incorrect because acidic solutions generally have pH below 7. B: Correct because at 25°C, pH values above 7 indicate a basic or alkaline solution. C: Incorrect because neutral water has pH 7 at 25°C. D: Incorrect because pure water is neutral at 25°C.
CSS - PMS - CCE - PCS - General Science
Acid/Base
At 25°C, a solution with pH less than 7 is generally:
A. Acidic
B. Basic
C. Neutral
D. Always a buffer
Correct Answer: A
A: Correct because at 25°C, pH values below 7 indicate an acidic aqueous solution. B: Incorrect because basic solutions generally have pH above 7. C: Incorrect because neutral water has pH 7 at 25°C. D: Incorrect because a buffer may be acidic or basic; pH below 7 does not always mean it is a buffer.
CSS - PMS - CCE - PCS - General Science
Acid/Base
A Lewis base is best described as:
A. Electron-pair donor
B. Electron-pair acceptor
C. Proton donor
D. Salt producer only
Correct Answer: A
A: Correct because a Lewis base donates an electron pair. B: Incorrect because electron-pair acceptance defines a Lewis acid. C: Incorrect because proton donation defines a Brønsted acid. D: Incorrect because many reactions form salts, but this is not the defining feature of a Lewis base.
CSS - PMS - CCE - PCS - General Science
Acid/Base
A Lewis acid is best described as:
A. Electron-pair donor
B. Electron-pair acceptor
C. Proton donor only
D. Hydroxide-ion donor
Correct Answer: B
A: Incorrect because electron-pair donation defines a Lewis base. B: Correct because a Lewis acid accepts an electron pair to form a coordinate bond. C: Incorrect because Lewis acids are broader than proton donors only. D: Incorrect because hydroxide donation is not the Lewis-acid definition.
CSS - PMS - CCE - PCS - General Science
Acid/Base
A Brønsted–Lowry base is a substance that:
A. Donates a proton
B. Accepts a proton
C. Produces H⁺ only
D. Accepts neutrons
Correct Answer: B
A: Incorrect because proton donation defines a Brønsted–Lowry acid. B: Correct because a Brønsted–Lowry base accepts a proton. C: Incorrect because producing H⁺ is not the definition of a Brønsted base. D: Incorrect because neutron acceptance is unrelated to acid–base chemistry.
CSS - PMS - CCE - PCS - General Science
Acid/Base
A Brønsted–Lowry acid is a substance that:
A. Accepts a proton
B. Donates a proton
C. Accepts an electron pair
D. Produces only OH⁻
Correct Answer: B
A: Incorrect because proton acceptance defines a Brønsted–Lowry base. B: Correct because a Brønsted–Lowry acid donates a proton, H⁺, to another species. C: Incorrect because electron-pair acceptance defines a Lewis acid. D: Incorrect because production of OH⁻ is associated with Arrhenius bases.
CSS - PMS - CCE - PCS - General Science
Acid/Base
According to Arrhenius, a base produces which ion in aqueous solution?
A. H⁺
B. OH⁻
C. Cl⁻
D. HCO₃⁻
Correct Answer: B
A: Incorrect because H⁺ characterizes an Arrhenius acid. B: Correct because an Arrhenius base increases the concentration of hydroxide ions in water. C: Incorrect because Cl⁻ is a spectator ion in many reactions. D: Incorrect because HCO₃⁻ can act as a base but is not the defining Arrhenius ion.
CSS - PMS - CCE - PCS - General Science
Acid/Base
According to Arrhenius, an acid produces which ion in aqueous solution?
A. H⁺
B. OH⁻
C. Na⁺
D. Cl⁻
Correct Answer: A
A: Correct because an Arrhenius acid increases the concentration of hydrogen ions, more accurately hydronium ions, in water. B: Incorrect because OH⁻ is produced by Arrhenius bases. C: Incorrect because Na⁺ is a common metal ion, not the defining acidic ion. D: Incorrect because Cl⁻ may accompany H⁺ in HCl but does not define an acid.
CSS - PMS - CCE - PCS - General Science
Periodic Table - Metals & Non-metals
Which metal is liquid at room temperature?
A. Iron
B. Mercury
C. Copper
D. Aluminium
Correct Answer: B
B: Correct because mercury is a metal that is liquid at room temperature. A: Wrong because iron is solid. C: Wrong because copper is solid. D: Wrong because aluminium is solid.
CSS - PMS - CCE - PCS - General Science
Organs
The largest organ of the human body is:
A. Heart
B. Skin
C. Brain
D. Liver
Correct Answer: B
B: Correct because skin is the largest organ by surface area and mass. A: Wrong because the heart is muscular pump. C: Wrong because brain is control center but not largest organ. D: Wrong because liver is large internal organ but smaller than skin.
CSS - PMS - CCE - PCS - General Science
Gases
Which gas do humans exhale in greater amount than they inhale?
A. Oxygen
B. Carbon dioxide
C. Nitrogen only
D. Helium
Correct Answer: B
B: Correct because cellular respiration produces carbon dioxide, so exhaled air has more CO2. A: Wrong because oxygen is consumed by the body. C: Wrong because nitrogen is mostly unchanged. D: Wrong because helium is not produced by the body.
CSS - PMS - CCE - PCS - General Science
DNA
DNA stands for:
A. Deoxyribonucleic Acid
B. Dynamic Nuclear Atom
C. Digital Network Access
D. Double Nitrogen Acid
Correct Answer: A
A: Correct because DNA is Deoxyribonucleic Acid, the hereditary material. B: Wrong because dynamic nuclear atom is not biology terminology. C: Wrong because digital network access is computing-related. D: Wrong because double nitrogen acid is incorrect.
CSS - PMS - CCE - PCS - General Science
Scientific Instruments
Which instrument measures temperature?
A. Barometer
B. Thermometer
C. Hygrometer
D. Ammeter
Correct Answer: B
B: Correct because a thermometer measures temperature. A: Wrong because barometer measures air pressure. C: Wrong because hygrometer measures humidity. D: Wrong because ammeter measures electric current.
CSS - PMS - CCE - PCS - General Science
Mechanics - Force
Which force pulls objects toward Earth?
A. Magnetic force
B. Gravitational force
C. Friction only
D. Electric force only
Correct Answer: B
B: Correct because gravity attracts objects toward Earth's centre. A: Wrong because magnetism acts on magnetic materials. C: Wrong because friction opposes motion between surfaces. D: Wrong because electric force acts between charges.
CSS - PMS - CCE - PCS - General Science
Vitamins
Which disease is caused by deficiency of vitamin C?
A. Rickets
B. Scurvy
C. Goitre
D. Night blindness
Correct Answer: B
B: Correct because scurvy is caused by vitamin C deficiency. A: Wrong because rickets is linked to vitamin D deficiency. C: Wrong because goitre is commonly linked to iodine deficiency. D: Wrong because night blindness is linked to vitamin A deficiency.
CSS - PMS - CCE - PCS - General Science
Chemical Reactions - Salts
Boiling point of pure water at sea level is:
A. 0°C
B. 50°C
C. 100°C
D. 200°C
Correct Answer: C
C: Correct because pure water boils at 100°C at standard atmospheric pressure. A: Wrong because 0°C is freezing point. B: Wrong because 50°C is below normal boiling point. D: Wrong because 200°C is too high at sea level.
CSS - PMS - CCE - PCS - General Science
Parts of Plant
Which part of the plant absorbs water from soil?
A. Flower
B. Root
C. Fruit
D. Leaf only
Correct Answer: B
B: Correct because roots absorb water and minerals from soil. A: Wrong because flowers are reproductive parts. C: Wrong because fruits protect seeds. D: Wrong because leaves mainly do photosynthesis.
CSS - PMS - CCE - PCS - General Science
Acid/Base
Acid turns blue litmus paper:
A. Red
B. Green
C. Black
D. White
Correct Answer: A
A: Correct because acids turn blue litmus red. B: Wrong because green is not the acid response. C: Wrong because black is not a litmus result. D: Wrong because white is not a litmus result.
CSS - PMS - CCE - PCS - General Science
Blood System
Which blood cells fight infections?
A. Red blood cells
B. White blood cells
C. Platelets
D. Plasma only
Correct Answer: B
B: Correct because white blood cells are part of the immune response. A: Wrong because red cells transport oxygen. C: Wrong because platelets help clotting. D: Wrong because plasma is the fluid part of blood.