Search SchoolNGR

Sunday, 21 June 2026
Register . Login

Chemistry Past Questions and Answers

Topic: The mole concept and Avogadro's number

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

Question 16:
16.8 g of sodium hydrogen trioxocarbonate (IV) is completely decomposed by heat. Calculate the volume of carbon(IV) oxide given off s.t.p
[Na 23, C = 12, O = 16, H = 1, Molar volume of a gas at s.t.p = 22.4 dm3]
  • A 22.40 dm<sup style='font-size: smaller;'>3</sup>
  • B 11.20 dm<sup style='font-size: smaller;'>3</sup>
  • C 2.24 dm<sup style='font-size: smaller;'>3</sup>
  • D 1.12 dm<sup style='font-size: smaller;'>3</sup>
View Answer & Explanation
Question 17:
A hydrocarbon X with a molar mass of 26 consists of 92.3% carbon. What is its molecular formular
  • A C<sub style='font-size: smaller;'>2</sub>H<sub style='font-size: smaller;'>2</sub>
  • B C<sub style='font-size: smaller;'>3</sub>H<sub style='font-size: smaller;'>3</sub>
  • C C<sub style='font-size: smaller;'>4</sub>H<sub style='font-size: smaller;'>4</sub>
  • D C<sub style='font-size: smaller;'>5</sub>H<sub style='font-size: smaller;'>5</sub>
View Answer & Explanation
Question 18:
0.0075 mole of calcium trioxocarbonate (IV) is added to 0.015 mole of a solution of hydrochloric acid. The volume of gas evolved at s.t.p is
[Molar volume of a gas at s.t.p = 22.4 dm3]
  • A 224cm<sup style='font-size: smaller;'>3</sup>
  • B 168cm<sup style='font-size: smaller;'>3</sup>
  • C 112cm<sup style='font-size: smaller;'>3</sup>
  • D 100cm<sup style='font-size: smaller;'>3</sup>
View Answer & Explanation
Question 19:
A compound contains 40.0% C, 6.7% H 53.3% O. If the molecular mass of the compound is 180, its molecular formula is [C =12, H =1,O]
  • 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;'>6</sub>O<sub style='font-size: smaller;'>3</sub>
  • D C<sub style='font-size: smaller;'>6</sub>H<sub style='font-size: smaller;'>12</sub>O<sub style='font-size: smaller;'>6</sub>
View Answer & Explanation
Question 20:
Calculate the volume in cm3 of oxygen evolved as s.t.p. when a current of 5 A is passed through acidified water for 193s
{F = 96500 Cmol-1, Molar volume of a gas at s.t.p. = 22.4 dm3}
  • A 224.000 dm<sup style='font-size: smaller;'>3</sup>
  • B 0.056 dm<sup style='font-size: smaller;'>3</sup>
  • C 0.224 dm<sup style='font-size: smaller;'>3</sup>
  • D 56.000 dm<sup style='font-size: smaller;'>3</sup>
View Answer & Explanation