BPSC CCE Prelims
Chemistry Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Chemistry
Topic Breakdown: Scroll →
Which among the following are constituents of brass?
Detailed Explanation:
Brass is an alloy composed primarily of copper (Cu) and zinc (Zn). The proportion of these two metals can vary (typically 55–95% copper, 5–45% zinc), affecting properties like color, hardness, and corrosion resistance.
Other options are incorrect: Iron and zinc do not form brass; copper and nickel form cupronickel; iron and copper is not a standard brass alloy.
Therefore, zinc and copper are the constituents of brass, making Option 4 the correct answer.
Which among the following is known as quicklime?
Detailed Explanation:
Quicklime is the common name for calcium oxide (CaO), produced by heating limestone (CaCO₃) to drive off carbon dioxide.
Ca(OH)₂ is slaked lime (formed when quicklime reacts with water), CaCl₂ is calcium chloride, and CaCO₂ is not a valid chemical formula.
Therefore, CaO is quicklime, making Option 4 the correct answer.
What happens to the weight of iron, when it rusts?
Detailed Explanation:
Rusting is oxidation of iron (4Fe + 3O₂ → 2Fe₂O₃·xH₂O), where oxygen and water molecules bond to iron atoms, increasing total mass as hydrated iron oxide forms.
Over time, the rust layer flakes off or detaches from the surface due to its brittle nature, causing the overall weight to decrease.
Therefore, the weight first increases (oxidation) then decreases (flaking), making Option 2 the correct answer.
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Which among the following is also known as white metal?
Detailed Explanation:
Platinum is a lustrous, dense, silver-white precious metal with high corrosion resistance and catalytic properties. It is commonly referred to as white metal due to its natural silvery-white appearance.
Gold is yellow, copper is reddish-brown, and cobalt is greyish-blue—none match the white metal descriptor. While industrial alloys of tin/lead are sometimes called "white metal," in UPSC/general knowledge context, platinum is the standard answer.
Therefore, platinum's silvery-white color makes Option 2 the correct answer.
Consider the following statements with respect to noble metals :
- Noble metals are found in pure form in nature.
- Uranium and lead are examples of noble metal.
Which of the above statements is/are correct?
Detailed Explanation:
Noble metals (gold, silver, platinum, and platinum-group metals) are chemically inert, resist corrosion, and are typically found in pure native form in nature due to their nonreactive properties.
- Statement 1 is Correct: Noble metals like gold and platinum occur naturally in uncombined, pure metallic state.
- Statement 2 is Incorrect: Uranium and lead are highly reactive metals that occur as ores (e.g., uraninite, galena), not as noble metals.
- Therefore, only Statement 1 is correct, making Option 4 the correct answer.
Consider the following statements :
- Addition of salt to pure water increases the boiling point of water and decreases the freezing point of water.
- When methyl alcohol is added to water boiling point of water decreases.
Which of the above statements is/are correct?
Detailed Explanation:
Salt (NaCl) is a non-volatile solute that causes boiling point elevation and freezing point depression through colligative properties—saltwater boils at a higher temperature and freezes at a lower temperature than pure water.
Methyl alcohol (methanol) is a volatile solute with higher vapor pressure than water. When added to water, it increases the overall vapor pressure of the mixture, causing the boiling point to decrease.
Therefore, both statements correctly describe opposite effects due to different solute types, making Option 3 the correct answer.
Which among the following would cause the bright red colour due to bursting of crackers?
Detailed Explanation:
Strontium compounds (like strontium carbonate) emit a bright red colour when heated in fireworks. The heat excites electrons in strontium atoms, which release energy as red light when returning to ground state.
Sodium produces yellow, sulphur burns but doesn't produce metal flame colours, and magnesium gives white light.
Therefore, strontium is responsible for bright red colour in crackers, making Option 4 the correct answer.
What is the law in which under the same above conditions of temperature and pressure, equal volumes of all gases contain equal number of molecules?
Detailed Explanation:
Avogadro's law states that under the same temperature and pressure, equal volumes of all gases contain equal number of molecules.
- Core Principle: Discovered by Amedeo Avogadro (1812), this fundamental gas law directly matches the question's description.
- Therefore, Avogadro's law is the correct answer, making Option 3 correct.
The mass number of a nucleus is
Detailed Explanation:
The mass number (A) of a nucleus is defined as the sum of protons and neutrons in the nucleus. It is a count (dimensionless integer), not the actual mass in kilograms or atomic mass units.
Option 2 incorrectly states "total mass" (which would have units); Option 3 is false—mass number is close to but not always more than atomic weight; Option 4 is absurd—mass number is always greater than atomic number (Z).
Therefore, Option 1 is the correct answer.
Which of the following is the main ingredient of cement?
Detailed Explanation:
Cement is manufactured using multiple key ingredients, making Option 5 the correct choice. The primary component is limestone (~60–65%), which provides calcium oxide. Silica clay (~20–25%) supplies silica, alumina, and iron oxide. Gypsum (~3–5%) is added post-burning to regulate setting time.
Since limestone, silica clay, and gypsum are all essential ingredients—not just one—the answer cannot be a single option.
Therefore, more than one ingredient is correct, making Option 5 the correct answer.
Isotopes of an element differ in
Detailed Explanation:
Isotopes are atoms of the same element with identical atomic numbers (same number of protons) but different mass numbers due to varying numbers of neutrons. For example, Carbon-12 and Carbon-14 both have 6 protons but differ in neutron count (6 vs 8), resulting in different mass numbers (12 vs 14).
The number of protons and electrons remains constant within isotopes of an element, as changing protons would create a different element entirely, and neutral atoms maintain equal protons and electrons.
Therefore, isotopes differ only in mass number, making Option 2 the correct answer.
The temperature point at which solid, liquid and gaseous states may stay together is known as
Detailed Explanation:
The triple point is a unique thermodynamic condition where all three phases of a substance—solid, liquid, and gas—coexist in equilibrium at a specific temperature and pressure.
Boiling point (liquid to gas), melting point (solid to liquid), and freezing point (liquid to solid) each involve transitions between only two phases, not all three simultaneously.
Therefore, the triple point is where all three states coexist, making Option 4 the correct answer.
Which among the following solutions has pH value more than 7?
Detailed Explanation:
pH scale measures acidity and basicity: pH < 7 indicates acidic, pH = 7 is neutral, and pH > 7 indicates basic (alkaline) solutions.
Basic solutions have excess hydroxide ions (OH⁻), resulting in pH values greater than 7. Examples include sodium hydroxide, potassium hydroxide, and ammonia solutions.
Therefore, only basic solutions have pH > 7, making Option 2 the correct answer.
Which among the following is an incorrect option?
Detailed Explanation:
Option 1 is Incorrect: Atoms are electrically neutral because protons (positive) are in the nucleus and electrons (negative) orbit outside it—electrons are NOT inside the nucleus.
Options 2, 3, and 4 are Correct: Electrons are negatively charged with negligible mass; atomic number equals proton count; isotopes have applications in nuclear energy, medicine (radiotherapy), and carbon-14 dating.
Therefore, more than one statement is incorrect/correct, making Option 5 the correct answer.
Select the incorrect statement out of the following
Detailed Explanation:
Acrylic is a synthetic polymer derived from petrochemicals (acrylonitrile), not cotton, and is known for its wool-like properties, not silk-like shine.
Rayon (viscose) is the fiber actually called artificial silk because it is derived from natural cellulose (wood pulp/cotton linters) and has a silk-like sheen and drape.
Option 1 is correct (cotton absorbs moisture for summer comfort), Option 2 is correct (polycarbonate is used in CDs for its transparency and durability), and Option 4 is correct (Teflon/PTFE provides non-stick coating).
Therefore, Statement 3 is incorrect as acrylic is not prepared from cotton nor called artificial silk, making Option 3 the correct answer.