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CAIE A-Level Chemistry AS 2.1 Relative Masses of Atoms and Molecules Questions

Practise defining and calculating relative isotopic, atomic, molecular and formula masses on the carbon-12 scale.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • define the unified atomic mass unit as one twelfth of the mass of one carbon-12 atom
  • distinguish relative isotopic mass from weighted relative atomic mass
  • calculate relative molecular or formula mass by summing the appropriate relative atomic masses

Covered syllabus points

2.1.1—Unified atomic mass unit2.1.2—Atomic mass, Ar, isotopic mass

Question 1

[Maximum number: 1]

Which sodium compound contains 74.2 % by mass of sodium?

A

sodium carbonate

B

sodium chloride

C

sodium hydroxide

D

sodium oxide

Question 2

[Maximum number: 1]

Which statement is correct?

A

The relative atomic mass of a 35Cl{ }^{35} \mathrm{Cl} atom is 35.5 .

B

The relative formula mass of CaCO3\mathrm{CaCO}_{3} is 100.1.

C

The relative isotopic mass of a 24Mg{ }^{24} \mathrm{Mg} atom is 24.3 .

D

The relative molecular mass of O2\mathrm{O}_{2} is 16.0.

Question 3

[Maximum number: 1]

Which sample contains the most iodine?

A

1 g of CaI2\mathrm{CaI}_{2}

B

1 g of KI

C

1 g of NaI

D

1 g of NH4I\mathrm{NH}_{4} \mathrm{I}

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