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Quantitative Chemistry Flashcards
Free GCSE and A Level Chemistry Revision Cards
Get confident with moles, Avogadro's number, concentration calculations, percentage yield, and titration. These free Chemistry flashcards cover all the key quantitative chemistry skills for GCSE and A Level.
Question
What is a mole?
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Answer
The SI unit for amount of substance. One mole contains 6.02 × 10²³ particles (Avogadro's number). Moles = mass ÷ molar mass.
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Question
What is Avogadro's number?
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Answer
6.02 × 10²³ — the number of atoms, molecules, or ions in one mole of a substance.
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Question
What is relative atomic mass (Ar)?
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Answer
The average mass of an atom of an element relative to 1/12 the mass of a carbon-12 atom. Takes into account the natural abundance of isotopes.
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Question
What is relative formula mass (Mr)?
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Answer
The sum of relative atomic masses of all atoms in a formula unit, e.g. Mr of H₂O = (2 × 1) + 16 = 18.
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Question
How do you calculate the number of moles from mass?
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Answer
Moles = mass (g) ÷ molar mass (g/mol). E.g. 36 g of water ÷ 18 g/mol = 2 moles.
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Question
What is concentration and how is it calculated?
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Answer
The amount of solute dissolved per unit volume of solution. Concentration (mol/dm³) = moles ÷ volume (dm³).
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Question
What is a limiting reagent?
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Answer
The reactant that is completely used up first in a reaction, limiting the amount of product that can be formed.
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Question
What is percentage yield?
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Answer
Percentage yield = (actual yield ÷ theoretical yield) × 100. Actual yield is always ≤ theoretical due to losses, side reactions, or incomplete reactions.
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Question
What is atom economy?
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Answer
Atom economy = (molar mass of desired product ÷ total molar mass of all products) × 100. Measures how efficiently atoms in reactants are converted to useful products.
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Question
What is an empirical formula?
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Answer
The simplest whole-number ratio of atoms of each element in a compound. E.g. glucose (C₆H₁₂O₆) has empirical formula CH₂O.
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