Chemistry MCQs set 3 for GBPSC General Posts (Gilgit-Baltistan) Everyday Science — 20 solved questions.
Q1. The International System of Units (SI) has ___ base units of measurement.
Answer: Seven
Explanation: SI (Système International) defines exactly seven base units: metre, kilogram, second, ampere, kelvin, mole, and candela, from which all other units are derived.
Q2. A closed flask contains water in all its three states: solid, liquid, and vapor at 0°C. In this situation, the average K.E. of the water molecules will be:
Answer: The same in all three states
Explanation: At thermal equilibrium (0°C), all three states share the same temperature, so the average kinetic energy of molecules - which depends only on temperature - is identical across solid, liquid, and vapor.
Q3. In the process of photosynthesis, which gas is released?
Answer: Oxygen
Explanation: During photosynthesis, plants use carbon dioxide and water to produce glucose, releasing oxygen as a by-product through the light-dependent reactions.
Q4. Who proposed the chemical evolution of life?
Answer: Oparin
Explanation: Alexander Oparin proposed the chemical evolution theory of life's origin in his 1924 work, suggesting life arose from simple organic molecules in a primordial soup.
Q5. The rate of a chemical reaction depends on the nature of chemical reactants because:
Answer: The energy of activation differs from one reactant to another
Explanation: Different chemical reactants have different bond energies and electronic structures, resulting in different activation energies that directly determine how fast a reaction proceeds.
Q6. Frederick Banting, a Canadian physiologist, was famous for being the co-discoverer of ______.
Answer: insulin
Explanation: Frederick Banting, along with Charles Best, discovered insulin in 1921 at the University of Toronto, a breakthrough that transformed the treatment of diabetes.
Q7. Generally, in a given period in the periodic table, as we move from left to right, the electropositive character of elements:
Answer: Decreases
Explanation: Across a period from left to right, nuclear charge increases, pulling electrons more tightly and reducing the tendency to lose electrons, so electropositive (metallic) character decreases.
Q8. Which one of the following represents a chemical change?
Answer: Heating of mercuric oxide powder
Explanation: Heating mercuric oxide causes it to decompose into mercury and oxygen - a chemical reaction that produces new substances, which is the hallmark of a chemical change.
Q9. The chemical name of laughing gas is:
Answer: Nitrous oxide
Explanation: Laughing gas is nitrous oxide (N₂O); at low concentrations it induces a sense of euphoria and mild analgesia, which is why it earned this colloquial name.
Q10. Which of the following compounds would you most likely drink?
Answer: H2O
Explanation: H₂O is water, the only compound among the options that is safe to drink; the others are hydrochloric acid, sulfuric acid, and hydrogen peroxide.
Q11. What product, invented by William Shockley, John Bardeen, and Walter Brattain at Bell Labs in 1947, revolutionised the electronics industry?
Answer: Transistor
Explanation: Shockley, Bardeen, and Brattain invented the transistor at Bell Labs in 1947, replacing bulky vacuum tubes and revolutionizing electronics by enabling miniaturized circuits.
Q12. The chemical formula of washing soda is:
Answer: Na2CO3
Explanation: Na2CO3 is the scientifically accurate choice. The concept tested here is core everyday science for MDCAT, ECAT, and general ability papers.
Q13. Diamonds are made up almost entirely of which element?
Answer: Carbon
Explanation: Diamond is an allotrope of carbon, composed almost entirely of carbon atoms arranged in a crystal lattice structure, giving it extreme hardness.
Q14. Which of the following solutions can be used as electrolytes?
Answer: Sodium Chloride (NaCl)
Explanation: Sodium chloride (NaCl) dissociates into Na⁺ and Cl⁻ ions in solution, making it an ionic conductor (electrolyte); sugar, urea, and distilled water do not ionize significantly.
Q15. Nuclear radiation is emitted by those elements whose:
Answer: Nuclei are unstable
Explanation: Radioactive elements have unstable nuclei that spontaneously emit radiation (alpha, beta, or gamma) as they decay toward a more stable configuration.
Q16. The SI base unit for mass is the:
Answer: Kilogram
Explanation: The International System of Units (SI) defines the kilogram as the base unit of mass, originally defined by a platinum-iridium prototype and now by Planck's constant.
Q17. A branch of pharmacology dealing with poisons and other toxic substances is called:
Answer: Toxicology
Explanation: Toxicology is the branch of pharmacology and medicine that studies the adverse effects of chemical substances, poisons, and drugs on living organisms.
Q18. The elements in the first period of the periodic table are:
Answer: Hydrogen and helium
Explanation: The first period of the periodic table contains only hydrogen (atomic number 1) and helium (atomic number 2), corresponding to filling the 1s electron shell.
Q19. The transfer of thermal energy from one substance to another through which requires no physical medium:
Answer: Radiation
Explanation: Radiation is the scientifically accurate choice. The concept tested here is core everyday science for MDCAT, ECAT, and general ability papers.
Q20. Which of the following functions is performed by a photocell?
Answer: It converts light energy into electrical energy
Explanation: A photocell (photoelectric cell) converts light energy into electrical energy using the photoelectric effect, where photons eject electrons from a photosensitive material.