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General Science Quiz: Atoms and Molecules: Laws of Chemical Combination and the Mole Concept

  • 10 questions
  • 10 minutes
  • Difficulty: Medium
Useful for:SSCSSC CGLSSC CHSLSSC MTSUPSC Civil ServicesRRB NTPCRRB Group DRRB ALPState Exams
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About this quiz

This General Science quiz on Atoms and Molecules: Laws of Chemical Combination and the Mole Concept puts 10 multiple-choice questions to you, the verified MCQs published with GK24's note on the topic, 2 of them asked in real previous-year papers. Every question carries a full explanation of why the correct option is right and why the other options are wrong, so you learn the fact behind the answer rather than the letter. Attempt it right after reading the note, keep to the timer, and use the explanations at the end to mark what needs another look. Sit it again before the exam as a quick revision of the topic.

Questions in this quiz

10 questions with answers and explanations

Q1.General ScienceEasy

The law of conservation of mass in a chemical reaction was given by

  1. A.John Dalton
  2. B.Antoine Lavoisier
  3. C.Joseph Proust
  4. D.Amedeo Avogadro
Show answer
Correct answer: B. Antoine Lavoisier

The correct answer is B, Antoine Lavoisier, the French chemist who showed by careful weighing in closed vessels that the total mass of the products of a reaction is exactly equal to the total mass of the reactants, so that matter is neither created nor destroyed in a chemical change.

Q2.General ScienceMedium

The law which states that a pure chemical compound always contains the same elements combined in the same proportion by mass is known as

  1. A.The law of multiple proportions
  2. B.The law of constant proportions
  3. C.The law of conservation of mass
  4. D.The law of gaseous volumes
Show answer
Correct answer: B. The law of constant proportions

Water drawn from a river, from rain or made in a laboratory always has hydrogen and oxygen in the mass ratio of one to eight, and ammonia always has nitrogen and hydrogen in the ratio of fourteen to three.

Q3.General ScienceAsked in: RRB ALP · 17 Aug 2018, Shift 2Easy

Atomic mass of Nitrogen is 14 and that of Hydrogen is 1. What will be the molecular mass of Ammonia?

  1. A.17
  2. B.18
  3. C.15
  4. D.16
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Correct answer: A. 17

The formula of ammonia is NH3, so its molecular mass is the atomic mass of one nitrogen atom added to the atomic masses of three hydrogen atoms, that is fourteen plus three times one, which equals seventeen unified atomic mass units; one mole of ammonia therefore weighs seventeen grams.

Q4.General ScienceAsked in: RRB ALP · 27 Nov 2024, Shift 2Medium

The formula unit mass of CaCl2 is:

  1. A.115u
  2. B.114u
  3. C.111u
  4. D.110u
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Correct answer: C. 111u

Calcium chloride is an ionic compound, so the sum of the atomic masses in its formula is called the formula unit mass rather than the molecular mass.

Q5.General ScienceEasy

The number of particles present in one mole of any substance is

  1. A.6.022 into ten to the power twenty-three
  2. B.6.022 into ten to the power twenty-one
  3. C.3.011 into ten to the power twenty-three
  4. D.9.8 into ten to the power twenty-three
Show answer
Correct answer: A. 6.022 into ten to the power twenty-three

It is the number of atoms in twelve grams of carbon twelve, and it holds for atoms, molecules, ions or electrons alike, so one mole of water has that many water molecules and one mole of sodium has that many sodium atoms.

Q6.General ScienceMedium

At standard temperature and pressure, the volume occupied by one mole of any gas is

  1. A.11.2 litres
  2. B.22.4 litres
  3. C.24.4 litres
  4. D.1 litre
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Correct answer: B. 22.4 litres

It follows from Avogadro's law: since equal volumes of all gases at the same temperature and pressure contain an equal number of molecules, one mole of hydrogen, of oxygen or of carbon dioxide all take up the same space at standard temperature and pressure, even though their masses are two…

Q7.General ScienceMedium

One unified atomic mass unit, written as u, is defined as

  1. A.The mass of one hydrogen atom
  2. B.One twelfth of the mass of one atom of carbon twelve
  3. C.One sixteenth of the mass of one atom of oxygen
  4. D.The mass of one electron
Show answer
Correct answer: B. One twelfth of the mass of one atom of carbon twelve

This standard was adopted so that the atomic masses of all elements could be compared on one relative scale, and on it hydrogen comes out as about 1 u, oxygen as 16 u and chlorine as 35.5 u. Option A is wrong because the hydrogen atom was the standard in…

Q9.General ScienceHard

Carbon forms two oxides, carbon monoxide and carbon dioxide, in which twelve grams of carbon combines with sixteen grams and thirty two grams of oxygen respectively. This illustrates

  1. A.The law of conservation of mass
  2. B.The law of constant proportions
  3. C.The law of multiple proportions
  4. D.Avogadro's law
Show answer
Correct answer: C. The law of multiple proportions

When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other bear a simple whole number ratio, and here the oxygen masses of sixteen and thirty two grams for the same twelve grams of carbon are in the ratio…

Q10.General ScienceMedium

Equal volumes of all gases, under the same conditions of temperature and pressure, contain an equal number of molecules. This statement is known as

  1. A.Avogadro's law
  2. B.Boyle's law
  3. C.Charles's law
  4. D.Dalton's law of partial pressures
Show answer
Correct answer: A. Avogadro's law

It is the reason one mole of every gas occupies the same 22.4 litres at standard temperature and pressure, and it allowed chemists to settle the formulae of gases such as hydrogen and oxygen as having two atoms each.

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