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PPSC MCQs

Punjab Public Service Commission — Complete MCQ Bank

96 Questions
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21
Chemistry Medium

What is the chemical formula for sulfur dioxide a gas that causes acid rain?

  • ASO3
  • BS2O
  • CSO
  • DSO2
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Correct Answer: Option D — SO2
Explanation: Sulfur dioxide SO2 is produced by burning fossil fuels containing sulfur and when it reacts with atmospheric moisture it forms sulfurous and sulfuric acid contributing to acid rain.
Submitted by: PaperMCQs
22
Chemistry Easy

Which test is used to detect the presence of starch using iodine solution?

  • ABenedict's test
  • BBiuret test
  • CIodine test
  • DFlame test
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Correct Answer: Option C — Iodine test
Explanation: The iodine test detects starch by turning iodine solution from yellow-brown to blue-black in the presence of starch due to the triiodide ion fitting within the starch helix.
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23
Chemistry Medium

What is the chemical name of the compound with formula CuSO4?

  • ACopper sulfide
  • BCopper sulfite
  • CCopper carbonate
  • DCopper sulfate
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Correct Answer: Option D — Copper sulfate
Explanation: CuSO4 is copper sulfate a blue crystalline compound used in agriculture as a fungicide in electroplating and as a laboratory reagent for testing reducing sugars.
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24
Chemistry Medium

Which element is a semiconductor and is the main component of computer chips?

  • ACarbon
  • BGermanium
  • CSilicon
  • DGallium
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Correct Answer: Option C — Silicon
Explanation: Silicon is a semiconductor element with atomic number 14 and is the primary material used in computer chips integrated circuits and solar cells due to its controllable conductivity.
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25
Chemistry Medium

What is the chemical formula for washing soda used in cleaning?

  • ANaHCO3
  • BNaCl
  • CNa2CO3
  • DNaOH
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Correct Answer: Option C — Na2CO3
Explanation: Washing soda is sodium carbonate Na2CO3 a water softener and cleaning agent used to remove grease and stains and is also used in glass making and paper production.
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26
Chemistry Medium

What is the role of a catalyst in a chemical reaction?

  • AIncreases activation energy
  • BIs consumed by the reaction
  • CChanges the products formed
  • DIncreases reaction rate without being consumed
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Correct Answer: Option D — Increases reaction rate without being consumed
Explanation: A catalyst increases the rate of a chemical reaction by providing an alternative reaction pathway with lower activation energy and is not consumed or permanently changed during the process.
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27
Chemistry Medium

Which type of reaction absorbs energy from the surroundings causing the temperature to fall?

  • AEndothermic
  • BExothermic
  • CDisplacement
  • DCombustion
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Correct Answer: Option A — Endothermic
Explanation: Endothermic reactions absorb energy from their surroundings causing a temperature decrease as more energy is required to break bonds in reactants than is released forming products.
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28
Chemistry Medium

Which type of reaction releases energy to the surroundings causing the temperature to rise?

  • AEndothermic
  • BReversible
  • CEquilibrium
  • DExothermic
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Correct Answer: Option D — Exothermic
Explanation: Exothermic reactions release energy to the surroundings causing a temperature rise as bonds formed in products are stronger than bonds broken in reactants such as combustion.
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29
Chemistry Easy

What is the SI unit of the amount of substance in chemistry?

  • AGram
  • BLitre
  • CKilogram
  • DMole
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Correct Answer: Option D — Mole
Explanation: The Mole is the SI unit for the amount of substance and one mole of any substance contains approximately 6.022 x 10 to the power 23 particles.
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30
Chemistry Medium

Which type of chemical formula shows the simplest whole number ratio of atoms in a compound?

  • AMolecular formula
  • BStructural formula
  • CDisplayed formula
  • DEmpirical formula
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Correct Answer: Option D — Empirical formula
Explanation: An empirical formula shows the simplest whole number ratio of each type of atom in a compound for example glucose C6H12O6 has the empirical formula CH2O.
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