1. Atom economy Glossary Alternative: Atom utilisation
A way of measuring what percentage of the mass of all the atoms in the reactants ends up in the desired product.
Atom economy =
100 x sum of relative formula mass of desired product from equation sum of relative masses of all reactants from equation
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2. Avogadro constant Glossary
The number of atoms, molecules or ions in one mole of a given substance (the value of the
Avogadro constant is 6.02 × 1023).
Extension: The value of the Avogadro constant was chosen so that the mass of one mole of that substance is equal to the relative formula mass (Mr) in grams.
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3. Burette Glossary
A glass tube with a tap and scale for measuring liquids to the nearest 0.1 cm3.
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4. Concordant Glossary Results that are very close together.
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5. Conservation of mass Glossary
In a reaction, the total mass of the reactants must
equal the total mass of the products.
Remember: All chemical reactions obey the law of conservation of mass.
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6. End point Glossary
The moment when the indicator changes colour in a titration showing that the moles of acid and
alkali are equal.
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7. Excess Glossary
When the amount of a reactant is greater than the amount that can react.
Remember: In many reactions involving two reactants, it is very common for an excess of one of the reactants to be used to ensure that all of the other reactant is used up.
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8. Limiting reactant Glossary
The reactant in a reaction that determines the amount of products formed. Any other reagents
are in excess and will not all react.
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9. Mole Glossary Measurement of the amount of a substance.
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10. Percentage yield Glossary
The amount of product formed in a reaction compared to the maximum theoretical mass that
could be produced as a percentage.
Percentage yield = mass of product actually made maximum theoretical mass of product ×100
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11. Pipette Glossary
A glass tube used to measure volumes of liquids with a very small margin of error.
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12. Relative atomic mass Glossary
The relative atomic mass (Ar) of an element is the average mass of atoms of that element taking into account the mass and amount of each isotope it contains on a scale where the mass of a 12C atom is 12.
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13. Relative formula mass Glossary
The sum of the relative atomic masses of all the atoms shown in the formula (often
referred to as formula mass).
Example: the formula of water is H2O and so the relative formula mass is the sum of the relative atomic mass of two hydrogen atoms (2 × 1) and one oxygen atom (16) which adds up to 18.
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14. Thermal decomposition Glossary
Reaction where heat causes a substance to
break down into simpler substances.
Example: Metal carbonates decompose into a metal oxide and carbon dioxide when heated.
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15. Yield Glossary The amount of product formed in a reaction.
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