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FPSC MCQs

Federal Public Service Commission — Complete MCQ Bank

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221
Chemistry Medium

What is the chemical formula for calcium hydroxide also known as slaked lime?

  • ACaO
  • BCaCO3
  • CCa(OH)2
  • DCaCl2
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Correct Answer: Option C — Ca(OH)2
Explanation: Calcium hydroxide Ca(OH)2 also called slaked lime is made by adding water to quicklime CaO and is used in construction water treatment and to neutralise acidic soils.
Submitted by: PaperMCQs
222
Chemistry Medium

Which acid is used in car batteries as the electrolyte?

  • ASulfuric acid
  • BHydrochloric acid
  • CNitric acid
  • DAcetic acid
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Correct Answer: Option A — Sulfuric acid
Explanation: Sulfuric acid H2SO4 is used as the electrolyte in lead-acid car batteries where it facilitates the electrochemical reactions between lead electrodes to store and release electrical energy.
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223
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.
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224
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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225
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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226
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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227
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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228
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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229
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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230
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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