1:28 understand how to carry out calculations involving amount of substance, relative atomic mass (Aᵣ) and relative formula mass (Mᵣ)

1:28 understand how to carry out calculations involving amount of substance, relative atomic mass (Aᵣ) and relative formula mass (Mᵣ)

The following formula allows for the interconversion between a mass in grams and a number of moles for a given substance:

    \[Amount(mol) = \frac{mass(g)}{M_r} \]

Example 1:

Calculate the amount, in moles, of 8.8 g of carbon dioxide (CO2).

Step 1: Calculate the relative formula mass (Mr) of carbon dioxide (CO2).

    \[Carbon\,dioxide = CO_2 \]

    \[Atoms\,present = (1 \times C) + (2 \times O) \]

    \[M_r = (1 \times 12) + (2 \times 16) = 44 \]

Step 2: Use the formula to calculate the amount in moles.

    \[Amount = \frac{mass(g)}{M_r} \]

    \[Amount = \frac{8.8}{44} \]

    \[Amount = 0.2 mol \]

Example 2:

Calculate the mass of 2 mol of copper(II) sulfate (CuSO4).

Step 1: Calculate the relative formula mass (Mr) of copper(II) sulfate (CuSO4).

    \[copper(II)\,sulfate = CuSO_4 \]

    \[Atoms\,present = (1 \times Cu) + (1 \times S) + (4 \times O) \]

    \[M_r = (1 \times 63.5) + (1 \times 32) + (4 \times 16) = 159.5 \]

Step 2: Rearrange the formula to calculate the mass.

    \[mass = amount \times M_r \]

    \[mass = 2 \times 159.5 \]

    \[mass = 319g\]

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Section 1: Principles of chemistry

      a) States of matter

      b) Atoms

      c) Atomic structure

     d) Relative formula masses and molar volumes of gases

     e) Chemical formulae and chemical equations

     f) Ionic compounds

     g) Covalent substances

     h) Metallic crystals

     i) Electrolysis

 Section 2: Chemistry of the elements

     a) The Periodic Table

     b) Group 1 elements: lithium, sodium and potassium

     c) Group 7 elements: chlorine, bromine and iodine

     d) Oxygen and oxides

     e) Hydrogen and water

     f) Reactivity series

     g) Tests for ions and gases

Section 3: Organic chemistry

     a) Introduction

     b) Alkanes

     c) Alkenes

     d) Ethanol

Section 4: Physical chemistry

     a) Acids, alkalis and salts

     b) Energetics

     c) Rates of reaction

     d) Equilibria

Section 5: Chemistry in industry

     a) Extraction and uses of metals

     b) Crude oil

     c) Synthetic polymers

     d) The industrial manufacture of chemicals