Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
The Alkali Metals
85 practice questions
Topics covered
Practice questions
41–50 of 85
Question 41
2 marks · Easy
Answer and see the solution →Explain why potassium dichromate(VI) is orange, while most compounds of sodium are white or colourless.
Question 42
3 marks · Easy
Answer and see the solution →A student observes three alkali metals exposed to air. The table shows her results.
Metal Time for surface to become dull / min Lithium 8 Sodium 4 Potassium 1 (a)[1 mark]Which metal reacts fastest with air?
(b)[1 mark]Which metal reacts slowest with air?
(c)[1 mark]State the trend in reactivity of these metals with air.
Question 43
1 mark · Easy
Answer and see the solution →State the usual colour of potassium bromide crystals.
Question 44
3 marks · Easy
Answer and see the solution →Describe what you would observe and name the product when sodium is heated strongly in air.
(a)[1 mark]State the colour of the flame when sodium burns.
(b)[1 mark]What is the appearance of the solid product formed?
(c)[1 mark]Name the compound produced in this reaction.
Question 45
2 marks · Easy
Answer and see the solution →A student heats a piece of potassium weighing 3.9 g in air. Potassium reacts fully to form potassium oxide (K$_2$O) according to the equation:
Calculate the maximum mass of potassium oxide formed from 3.9 g of potassium. (Relative atomic masses: K = 39, O = 16)
Question 46
2 marks · Easy
Answer and see the solution →A student dissolves 5.1 g of sodium chloride in water. Sodium chloride is a typical Group 1 metal compound. (Relative atomic masses: Na = 23, Cl = 35.5)
Calculate the number of moles of sodium chloride dissolved.
Question 47
2 marks · Normal
Answer and see the solution →Describe what you would observe when freshly cut pieces of sodium and potassium are exposed to air.
Question 48
4 marks · Normal
Answer and see the solution →The compounds of lithium, sodium, and potassium often appear similar.
(a)[1 mark]State the usual colours of lithium chloride, sodium chloride, and potassium chloride.
(b)[1 mark]Explain why solutions of these compounds are colourless.
(c)[1 mark]State their typical solubility in water.
(d)[1 mark]Give the formula for each of the following: (i) sodium oxide (ii) potassium oxide
Question 49
3 marks · Normal
Answer and see the solution →Most group 1 metal compounds are described as colourless or white and are soluble in water.
(a)[2 marks]Explain why compounds of lithium, sodium, and potassium with colourless anions appear colourless or white.
(b)[1 mark]Suggest why potassium permanganate(VII) solution is purple while sodium chloride solution is colourless.
Question 50
4 marks · Normal
Answer and see the solution →Three students set up an experiment to observe how quickly different alkali metals react with air. Each student cut a fresh piece of either lithium, sodium, or potassium, put it onto a clean white tile, and timed how long it took to lose its shiny appearance (tarnish). The results:
Time for shiny appearance to disappear after cutting (room temperature, seconds) Metal Time (s) Lithium 65 Sodium 24 Potassium 8 (a)[1 mark]Complete the following order of reactivity of the metals with air, from least to most reactive:
________ < ________ < ________
(b)[2 marks]Use the data to explain your answer to part (a).
(c)[1 mark]State the white solid formed when sodium reacts with oxygen in air.