BRAINCAKE

Amount of Substance

AQA AS-level ChemistryTopic 2 of 1333 lessons

Revision notes for Amount of Substance in AQA Chemistry (7404). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.

  1. Relative Atomic MassBecause most elements have more than one isotope and naturally occurring elements have different proportions of each isotope, the relative atomic…
  2. Relative Molecular MassThe relative molecular mass is the weighted mean mass of a molecule compared to 1/12th the mass of a carbon-12 atom.
  3. Relative Formula MassThe relative formula mass is the mass of a formula unit compared to 1/12th the mass of a carbon-12 atom.
  4. The Mole and The Avogadro ConstantThe easiest way of counting how many particles there are in a substance is to find its mass.
  5. Calculating the Number of MolesThe molar mass is the mass of one mole of any substance in grams and is given the symbol M.
  6. Example Question - 1When heated, a sample of potassium chlorate(V) (KClO3) produced 0.0897g of oxygen 2KClO3(s) → 2KCl(s) + 3O2(g) What is the amount, in moles, of…
  7. Example Question - 2Fe2O3(s) + 3CO(g) → 3CO2(g) + 2Fe(s) Calculate the mass of iron produced from 1000 tonnes of Fe2O3. mass of Fe2O3 = 1 × 109g moles of Fe2O3 = 1 ×…
  8. Mass ConcentrationThe concentration in g/dm3 is called the mass concentration.
  9. Example Question - 1The mass concentration in gdm-3 is mass &div volume in dm-3 To convert the volume from cm3 to dm3 you divide by 1000.
  10. Example Question - 2Solid calcium hydroxide reacts with nitric acid to form calcium nitrate.
  11. Molar ConcentrationsThe mole concentration of a solution is the amount of solute in moles dissolved in each 1 dm3.
  12. Example Question - 1An error is the difference between the experimental value and the accepted or correct value.
  13. Example Question - 2A 0.11g sample of pure barium was added to 100cm3 of water.
  14. The Ideal Gas EquationThe molecules that make up an ideal gas are in constant random motion.
  15. Finding the Number of Moles of GasHow many moles of nitrogen gas are present in 100cm3 at a temperature of 20.0°C and a pressure of 100kPa?
  16. Finding the Relative Molecular Mass of a GasYou can find the relative molecular mass of a gas by finding the mass of one mole of gas.
  17. Example Question - 1Sulfur dioxide reacts with oxygen to form sulfur trioxide.
  18. Example Question - 2A student determined the relative molecular mass, Mr, of an unknown volatile liquid Y in an experiment as shown in the diagram.
  19. Empirical FormulaThe empirical formula is the simplest whole number ratio of atoms of each element in a compound.
  20. Example Question - 1The empirical formula can be calculated using chemical analysis to determine the mass of each element in a compound or the percentage composition by…
  21. Example Question - 2The empirical formula can be calculated using chemical analysis to determine the mass of each element in a compound or the percentage composition by…
  22. Molecular FormulaThe empirical formula is the simplest whole number ratio of atoms of each element in a compound.
  23. Combustion AnalysisCombustion analysis can be used to find the composition by mass of compounds.
  24. Example Question - 10.500g of an organic compound X containing only carbon, hydrogen and oxygen, produces 0.733g of carbon dioxide and 0.300g of water on complete…
  25. Example Question - 20.10000g of an amino acid produced 0.11710g of carbon dioxide and 0.05992g of water.
  26. Balancing EquationsThe law of conservation of mass states that atoms cannot be created or destroyed.
  27. Ionic EquationsSome equations can be simplified by considering the ions present.
  28. TitrationsA titration is an analytical and quantitative technique to determine the volume of one solution that exactly reacts with a known volume of another…
  29. Titration CalculationsA titration is a technique where a solution of known concentration is used to determine the concentration of an unknown solution.
  30. Example Question - 1In a titration 25.0cm3 of 0.040moldm-3 of aqueous metal hydroxide exactly neutralises a 20.0cm3 0.1moldm-3 sample of sulfuric acid.
  31. Example Question - 2This question is about a white solid, MHCO3, that dissolves in water and reacts with hydrochloric acid to give a salt.
  32. Atom EconomySustainability is the ability to exist constantly in a balanced environment.
  33. Percentage YieldTheoretical calculations assume all the reactants are converted into products and calculate the maximum possible amount of product or the…

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