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31
Chemistry Medium

Which element is essential for the structure of DNA and RNA molecules alongside carbon hydrogen oxygen and nitrogen?

  • ASulfur
  • BCalcium
  • CIron
  • DPhosphorus
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Correct Answer: Option D — Phosphorus
Explanation: Phosphorus is a key element in DNA and RNA molecules forming the phosphate backbone of the double helix structure and is also essential in ATP the cell's energy currency.
Submitted by: PaperMCQs
32
Chemistry Medium

Which chemical process is used to extract metals from their ores using carbon or electrolysis?

  • AReduction
  • BOxidation
  • CNeutralisation
  • DChromatography
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Correct Answer: Option A — Reduction
Explanation: Reduction is used to extract metals from their ores by removing oxygen using a reducing agent like carbon or by electrolysis for more reactive metals like aluminium.
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33
Chemistry Medium

Which type of chemical bond exists between water molecules causing its unusually high boiling point?

  • ACovalent bond
  • BHydrogen bond
  • CIonic bond
  • DVan der Waals force
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Correct Answer: Option B — Hydrogen bond
Explanation: Hydrogen bonds between water molecules are responsible for water's unusually high boiling point surface tension and many other unique properties essential for life.
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34
Chemistry Medium

Which isotope of carbon is used in radiocarbon dating?

  • ACarbon-12
  • BCarbon-13
  • CCarbon-11
  • DCarbon-14
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Correct Answer: Option D — Carbon-14
Explanation: Carbon-14 is a radioactive isotope used in radiocarbon dating of organic materials because it decays at a known rate allowing scientists to estimate the age of ancient samples.
Submitted by: PaperMCQs
35
Chemistry Medium

What is an isotope?

  • AAtoms of different elements with the same mass
  • BAtoms of the same element with different numbers of protons
  • CAtoms of the same element with the same number of protons but different neutrons
  • DAtoms of different elements with the same electrons
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Correct Answer: Option C — Atoms of the same element with the same number of protons but different neutrons
Explanation: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons resulting in different mass numbers but similar chemical properties.
Submitted by: PaperMCQs
36
Chemistry Hard

Which element has the highest electronegativity on the Pauling scale?

  • AOxygen
  • BChlorine
  • CNitrogen
  • DFluorine
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Correct Answer: Option D — Fluorine
Explanation: Fluorine has the highest electronegativity of all elements at 3.98 on the Pauling scale due to its small atomic size and high effective nuclear charge on its outer electrons.
Submitted by: PaperMCQs
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