IB Chemistry SL 1.4.2 Relative Atomic and Formula Mass

Practise defining relative atomic mass against the carbon-12 standard and calculating relative formula mass from atomic data. Include every atom in molecular, ionic and hydrated…

Exam points

define relative atomic mass as a weighted mean relative to one-twelfth of carbon-12
sum all atomic contributions, including water of crystallisation, to determine Mr
use reacting masses and a formula ratio to deduce an unknown relative atomic mass

[Maximum number: 1]

The element boron has two naturally occurring isotopes, ${ }^{10} \mathrm{~B}$ and ${ }^{11} \mathrm{~B}$ .

The percentage abundance of the isotopes of boron can be determined with a mass spectrometer. The diagram shows the operation of a mass spectrometer.

Figure for Question 1.4.2—Relative atomic mass (Ar) and relative formula mass (Mr) question 1 — IB Chemistry SL

Identify the species that is used as the scale for the mass of the isotopes.

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1.4.2—Relative atomic mass (Ar) and relative formula mass (Mr) question 1