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Sunday, 21 June 2026
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Chemistry Past Questions and Answers

Topic: The mole concept and Avogadro's number

Jamb Chemistry Questions - The mole concept and Avogadro's number

Question 21:
A gas X diffuses twice as fast as gas Y. if the relative molecular mass of X is 32, calculate the relative molecular mass of Y.
  • A 128
  • B 8
  • C 16
  • D 64
View Answer & Explanation
Question 22:
A fixed mass of gas a volume of 92cm3 at 3°C. When will be its volume at 18C if the pressure remains constant?
  • A 15.3cm<sup style='font-size: smaller;'>3</sup>
  • B 87.3cm<sup style='font-size: smaller;'>3</sup>
  • C 2.0cm<sup style='font-size: smaller;'>3</sup>
  • D 97.0cm<sup style='font-size: smaller;'>3</sup>
View Answer & Explanation
Question 23:
A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, Find the molecular formula [H = 1, C = 12, O = 16)
  • A CH<sub style='font-size: smaller;'>2</sub>O
  • B C<sub style='font-size: smaller;'>3</sub>H<sub style='font-size: smaller;'>6</sub>O<sub style='font-size: smaller;'>3</sub>
  • C C<sub style='font-size: smaller;'>6</sub>H<sub style='font-size: smaller;'>12</sub>O<sub style='font-size: smaller;'>6</sub>
  • D C<sub style='font-size: smaller;'>6</sub>H<sub style='font-size: smaller;'>12</sub>O<sub style='font-size: smaller;'>3</sub>
View Answer & Explanation
Question 24:
Calculate the volume in cm3 of oxygen evolved at s.t.p when a current of 5A is passed through acidified water for 193s?
[F = 96500 C mol1. Molar volume of a gas at s.t.p = 22.4dm3]
  • A 0.056dm<sup style='font-size: smaller;'>3</sup>
  • B 0.224dm<sup style='font-size: smaller;'>3</sup>
  • C 224.000dm<sup style='font-size: smaller;'>3</sup>
  • D 56.000dm<sup style='font-size: smaller;'>3</sup>
View Answer & Explanation
Question 25:
At 27°C, 58.5g of sodium chloride is present in 250cm\(^3\) of a solution. The solubility of sodium chloride at this temperature is?
(molar mass of sodium chloride = 111.0gmol\(^{-1}\))
  • A 2.0 moldm\(^{-3}\)
  • B 0.25 moldm\(^{-3}\)
  • C 1.0 moldm\(^{-3}\)
  • D 0.5 moldm\(^{-3}\)
View Answer & Explanation