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11
Chemistry Hard

Which element in Group 1 of the periodic table reacts most vigorously with water?

  • ALithium
  • BSodium
  • CCaesium
  • DPotassium
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Correct Answer: Option C — Caesium
Explanation: Caesium the heaviest stable Group 1 alkali metal reacts most vigorously with water due to its large atomic radius and low ionisation energy resulting in an explosive reaction.
Submitted by: PaperMCQs
12
Chemistry Medium

Which type of organic reaction involves the addition of bromine water across a carbon to carbon double bond?

  • AAddition
  • BSubstitution
  • CElimination
  • DHydrolysis
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Correct Answer: Option A — Addition
Explanation: Addition reactions involve adding molecules across the carbon to carbon double bond of an alkene such as the decolourisation of bromine water used as a test for unsaturation.
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13
Chemistry Medium

What is formed when an alcohol reacts with a carboxylic acid?

  • AEster and water
  • BSalt and water
  • CSoap
  • DAlkene and water
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Correct Answer: Option A — Ester and water
Explanation: When an alcohol reacts with a carboxylic acid an esterification reaction occurs producing an ester and water and this reaction requires an acid catalyst such as concentrated sulfuric acid.
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14
Chemistry Medium

Which organic functional group is present in carboxylic acids?

  • AHydroxyl group
  • BCarboxyl group COOH
  • CCarbonyl group
  • DAmino group
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Correct Answer: Option B — Carboxyl group COOH
Explanation: The carboxyl group COOH is the functional group present in all carboxylic acids and is responsible for their acidic properties as it can donate a proton to a base.
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15
Chemistry Medium

Which organic functional group is present in alcohols?

  • ACarbonyl group
  • BHydroxyl group
  • CCarboxyl group
  • DAmino group
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Correct Answer: Option B — Hydroxyl group
Explanation: The hydroxyl group OH is the functional group present in all alcohols and is responsible for their characteristic properties such as being able to form hydrogen bonds with water.
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16
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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17
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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18
Chemistry Medium

What is the concentration of a solution measured in moles per litre called?

  • ANormality
  • BMolality
  • CFormality
  • DMolarity
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Correct Answer: Option D — Molarity
Explanation: Molarity is the measure of concentration of a solution expressed as the number of moles of solute dissolved per litre of solution with units of mol/L or M.
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19
Chemistry Medium

Which scientific law states that equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules?

  • ABoyle's Law
  • BGay-Lussac's Law
  • CAvogadro's Law
  • DCharles's Law
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Correct Answer: Option C — Avogadro's Law
Explanation: Avogadro's Law states that equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules regardless of the nature of the gas.
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20
Chemistry Hard

What is the chemical formula for potassium permanganate a strong oxidising agent?

  • AKMnO4
  • BK2MnO4
  • CK2SO4
  • DK2Cr2O7
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Correct Answer: Option A — KMnO4
Explanation: Potassium permanganate has the formula KMnO4 and is a strong oxidising agent used in water treatment as a disinfectant and in analytical chemistry as a titrating agent.
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