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Formulae, Equations and Amounts of Substance

  • 5 subtopics
  • 15 things to know
  • Unit AS 1

What Formulae, Equations and Amounts of Substance covers

Formulae, Equations and Amounts of Substance is examined in Unit AS 1, Basic Concepts in Physical and Inorganic Chemistry, and drawn on again in Unit AS 3, Basic Practical Chemistry. It covers ionic charges and the formulae of compound ions, writing and balancing full and ionic equations, the mole, molar mass and Avogadro's constant, reacting masses and reactants in excess and hydrated salts and water of crystallisation.

Where it is assessed

Unit AS 1

Basic Concepts in Physical and Inorganic Chemistry, and again in Unit AS 3, Basic Practical Chemistry.

Check the CCEA specification ↗

The 5 subtopics

Each one has its own page.

What you need to know

Answer each one before you reveal it.

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Key term

Explain why the molar mass of an element in g mol⁻¹ is numerically equal to its relative atomic mass.

Key term

9.75 g of zinc reacts with 3.20 g of sulfur to form zinc sulfide. Which reactant is in excess?

Numbers

Hydrated magnesium sulfate is found to be 51.1% water by mass. Calculate the number of moles of water of crystallisation.

Key term

How is the charge on a simple ion predicted from the position of its element in the Periodic Table?

Key term

What must be true of both sides of a correctly balanced chemical equation?

Key term

State the formula of the sulfate ion and of the sulfite ion.

Key term

Why can the formula of a compound never be altered to make an equation balance?

Key term

Define the mole.

Key term

Explain what a balanced equation tells a chemist about the amounts of substances reacting.

Key term

Define the term water of crystallisation.

Key term

Give the formula of the thiosulfate ion.

Key term

State the four state symbols and what each means.

Key term

Define Avogadro's constant and state its value.

Process

Describe the three steps used to calculate a reacting mass from a given mass.

Key term

What is meant by an anhydrous compound?

Take Formulae, Equations and Amounts of Substance further

The same content, four other ways.

Questions from this topic

Each one with the model answer underneath.

  1. 1

    How is the charge on a simple ion predicted from the position of its element in the Periodic Table?

    Model answer

    Elements in Groups I, II and III lose one, two or three electrons to form 1+, 2+ and 3+ ions, and elements in Groups V, VI and VII gain three, two or one electron to form 3−, 2− and 1− ions, in each case reaching a noble gas arrangement.

  2. 2

    State the formula of the sulfate ion and of the sulfite ion.

    Model answer

    The sulfate ion is SO₄²⁻ and the sulfite ion is SO₃²⁻.

  3. 3

    Give the formula of the thiosulfate ion.

    Model answer

    The thiosulfate ion is S₂O₃²⁻.

  4. 4

    What is the formula of the hydrogensulfate ion?

    Model answer

    The hydrogensulfate ion is HSO₄⁻.

  5. 5

    Give the formulae of the carbonate and hydrogencarbonate ions.

    Model answer

    The carbonate ion is CO₃²⁻ and the hydrogencarbonate ion is HCO₃⁻.

  6. 6

    What are the formulae of the nitrate and nitrite ions?

    Model answer

    The nitrate ion is NO₃⁻ and the nitrite ion is NO₂⁻.

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Formulae, Equations and Amounts of Substance
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Formulae, Equations and Amounts of Substance revision questions

What does Formulae, Equations and Amounts of Substance cover in CCEA A-Level Chemistry?
5 subtopics: ionic charges and the formulae of compound ions, writing and balancing full and ionic equations, the mole, molar mass and avogadro's constant, reacting masses and reactants in excess and hydrated salts and water of crystallisation. Each one has its own page with questions and model answers.
How is Formulae, Equations and Amounts of Substance organised?
By the CCEA 1110 specification, subtopic by subtopic, so it matches the order you are taught it in.

Every question in Formulae, Equations and Amounts of Substance, on a schedule.

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