IGCSE Chemistry Extended 12.5.4—Use of a flame test to identify the Topic Practice

• Describe use of a flame test to identify the cations: (a) lithium, Li+ (b) sodium, Na+ (c) potassium, K+ (d) calcium, Ca2+ (e) barium, Ba2+ (f) copper(II), Cu2+

[Maximum number: 1]

A list of substances is shown.
> barium nitrate carbon monoxide hydrated cobalt(II) chloride copper(II) oxide anhydrous copper(II) sulfate ethane potassium iodide propene sodium bromide sulfur dioxide zinc oxide

Answer the following questions using only the substances from the list. Each substance may be used once, more than once or not at all.

Give the name of the substance that:

gives a lilac colour in a flame test

[Maximum number: 1]

The names of the elements of Period 2 of the Periodic Table are shown.
lithium beryllium boron carbon nitrogen oxygen fluorine neon Answer the following questions about these elements. Each element may be used once, more than once or not at all.

Identify the element which:

produces a red flame in a flame test

[Maximum number: 3]

This question is about ions and ionic compounds.

(a)

Choose from the following list of ions to answer the questions.

Each ion may be used once, more than once or not at all.
State which ion:

[ 1 ]

(i)

gives a lilac colour in a flame test [1]

[ 1 ]

(b)

Describe how to do a flame test on a sample of a salt.

[ 2 ]

[Maximum number: 1]

Sodium is a reactive metal.

Sodium burns in air to form sodium oxide, $\mathrm{Na}_{2} \mathrm{O}$ .

State the colour of the flame seen when sodium burns.

[Maximum number: 1]

Potassium is a Group I element.

When potassium is added to water, it reacts vigorously and a coloured flame is seen. The equation for the reaction is shown.

2 \mathrm{~K}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 2 \mathrm{KOH}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})

State the colour of the flame seen.

[Maximum number: 3]

Calcium hydroxide, $\mathrm{Ca}(\mathrm{OH})_{2}$ , is slightly soluble in water.

Limewater is a saturated solution of calcium hydroxide, $\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{aq})$ .

Describe how you would test for the presence of calcium ions in a sample of limewater. test observations

[Maximum number: 1]

Potassium hydrogensulfate, $\mathrm{KHSO}_{4}$ , is an acid salt. It dissolves in water to produce an aqueous solution, X, containing $\mathrm{K}^{+}, \mathrm{H}^{+}$ and $\mathrm{SO}_{4}{ }^{2-}$ ions.

Describe what you would see when the following experiments are done.

A flame test is done on solution X.

[Maximum number: 1]

This question is about sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}$ , and salts that can be made from sulfuric acid.

Aqueous potassium hydrogensulfate, $\mathrm{KHSO}_{4}(\mathrm{aq})$ , contains the ions $\mathrm{K}^{+}(\mathrm{aq}), \mathrm{H}^{+}(\mathrm{aq})$ and $\mathrm{SO}_{4}{ }^{2-}(\mathrm{aq})$ .

Describe the observations in the following tests.

A flame test is carried out on aqueous potassium hydrogensulfate.

[Maximum number: 1]

Sodium hydrogensulfate, $\mathrm{NaHSO}_{4}$ , dissolves in water to produce an aqueous solution, X, containing $\mathrm{Na}^{+}, \mathrm{H}^{+}$ and $\mathrm{SO}_{4}{ }^{2-}$ ions.

State the observations when the following tests are done.

A flame test is carried out on X.

[Maximum number: 1]

A student carries out a flame test on a sample.
The flame colour observed is light green.
Which ion is present in the sample?

$\mathrm{Ba}^{2+}$

$\mathrm{Ca}^{2+}$

$\mathrm{Li}^{+}$

$\mathrm{K}^{+}$

0 selected

Question 1(a)

Question 1(f)

Question 1

Question 1(a)

Question 1(a)(i)

Question 1(b)

Question 2(b)(ii)

Question 2(c)(i)

Question 2(c)(iv)

Question 4(c)(ii)

Question 5(d)(i)

Question 5(c)(i)

Question 40