IGCSE Chemistry 1.17 Relative atomic mass Topic Practice

Be able to calculate the relative atomic mass of an element (Ar) from isotopic abundances

[Maximum number: 3]

Thallium, TI, is an element in Group 3 and Period 6 of the Periodic Table.
The atomic number of thallium is 81

A sample of thallium contains two isotopes.

The table shows the mass number and percentage abundance of each isotope in the sample.

Isotope	Mass number	Percentage abundance (%)
thallium-203	203	30.80
thallium-205	205	69.20

Calculate the relative atomic mass of this sample of thallium.

Give your answer to one decimal place.
relative atomic mass =

[Maximum number: 3]

A sample of neon contains two isotopes, ${ }^{20} \mathrm{Ne}$ and ${ }^{22} \mathrm{Ne}$

The relative abundances of the two isotopes in the sample are

{ }^{20} \mathrm{Ne} 91.2 \% \quad{ }^{22} \mathrm{Ne} 8.80 \%

Calculate the relative atomic mass of this sample of neon.
Give your answer to one decimal place.
(ii) Give the mass number of Z.
(iii) Give the letter of the species that is a positive ion. L

[Maximum number: 3]

The table gives some information about the halogens, chlorine, bromine and iodine.

Halogen	Physical state at room temperature	Colour
chlorine	gas	pale green
bromine	................................	red-brown
iodine	solid	................................

Chlorine has two isotopes of mass numbers 35 and 37.

The relative percentage of each isotope in a sample of chlorine is:
- chlorine-35: 77.78%
- chlorine-37: 22.22%

Calculate the relative atomic mass of this sample of chlorine.
Give your answer to one decimal place.

relative atomic mass = ................................

[Maximum number: 6]

This question is about the halogens.

(a)

A sample of bromine atoms contains 42.0% bromine- 79 and 58.0% bromine- 81. Calculate the relative atomic mass of this sample of bromine atoms.

Give your answer to three significant figures.
relative atomic mass =

[ 3 ]

(b)

A sample of chlorine contains 0.75 mol of ${ }^{35} \mathrm{Cl}$ atoms and 0.25 mol of ${ }^{37} \mathrm{Cl}$ atoms.

The table gives the relative molecular masses ( $M_{\mathrm{r}}$ ) of the different diatomic molecules of chlorine.

The table also gives the probability of having a molecule of ${ }^{37} \mathrm{Cl}^{37} \mathrm{Cl}$ in this sample.

[ 3 ]

(i)

Calculate the probability of having a molecule with an $M_{r}$ of 70
probability =

[ 1 ]

(ii)

Explain why the probability of a molecule having an $M_{\mathrm{r}}$ of 72 is not 0.1875

[ 2 ]

[Maximum number: 2]

The diagram represents an atom of boron.

Boron has two isotopes, boron-10 and boron-11.

A sample of boron contains 18.7% of boron-10 and 81.3% of boron-11.

Calculate the relative atomic mass of this sample of boron.

relative atomic mass = ................................

[Maximum number: 3]

Q and R represent isotopes of the same element.

A sample containing the isotopes Q and R has this percentage composition by mass.

Q = 20.6%
R = 79.4%

Calculate the relative atomic mass (Ar) of this sample of the element.
Give your answer to one decimal place.

Ar = ................................

[Maximum number: 2]

These are the symbols for the two isotopes of lithium.

A sample of lithium contains 7.5 % of ${ }_{3}^{6} \mathrm{Li}$ and 92.5 % of ${ }_{3}^{7} \mathrm{Li}$

Calculate the relative atomic mass $\left(A_{\mathrm{r}}\right)$ of this sample of lithium.

[Maximum number: 3]

The diagram shows the electronic configuration of an atom of an element.

(a) Complete the table by giving the missing information about this atom.

Information	Answer
name of the part of this atom labelled Z	................................
number of protons in this atom	................................
number of the group that contains this element	................................
number of the period that contains this element	................................
the charge on the ion formed from this atom	................................

This element has three isotopes.

The table shows the mass number and percentage abundance of each isotope in a sample of this element.

Mass number	Percentage abundance (%)
24	79.2
25	10.0
26	10.8

Calculate the relative atomic mass (Ar) of this element.
Give your answer to one decimal place.

relative atomic mass = ................................

[Maximum number: 3]

This question is about Group 2 elements and their compounds.

A sample of magnesium contains three isotopes.

Calculate the relative atomic mass $\left(A_{r}\right)$ of magnesium.

Give your answer to one decimal place.

A_{r}=

[Maximum number: 3]

The table shows the composition of a sample of a different element, Y, containing three isotopes.

Mass number of isotope	Percentage of isotope in sample
32	95.0
33	0.75
34	4.25

Using information from the table, calculate the relative atomic mass (Ar) of this sample of element Y.

Give your answer to one decimal place.

Ar = ................................

0 selected

Question 2(c)(ii)

Question 2(c)

Question 2(b)

Question 2

Question 2(c)

Question 2(d)

Question 2(d)(i)

Question 2(d)(ii)

Question 2(b)

Question 2(c)(ii)

Question 2(b)(ii)

Question 2(b)

Question 3(a)(ii)

Question 4(c)