Paper 1: Quantitive Chemistry

• State the law of conservation of mass

  During a chemical reaction, no atoms are made or destroyed, so the mass of their products is the same as the mass of the reactants
• What might be involved in a reaction is the mass of a reaction increases?

  
  

  Explain 2 reasons why mass may appear to increase in a reaction

  - Mass may appear to increase when one or more of the reactants is a gas that's found in air (eg. Oxygen) and when all the products are solids, liquids or aqueous

  
  

  
  

  - The particles in a gas move around and fill the space they're in. So before the reaction, the gas is floating around in the air. It's there but not contained in the reaction vessel, so you can't account for its mass

  
  

  - When the gas reacts to form part of the product, the particles become contained inside the reaction vessel - so the total mass of the stiff inside the reaction vessel increases
• Describe what happens to the mass when metal reacts with oxygen in a sealed container compared to an unsealed container

  - In an unsealed container - the mass would increase - as the mass of the metal oxides produced equals the total mass of the metals and oxygen that reacted from the air.

  
  

  - In a sealed container - the mass would stay the same as no particles go in or out the vessel
• When might the mass of the reactants decrease?

  The mass of a reaction may appear to decrease when one of the products is a gas and the reactants are reactants are solids, liquids and aqueous
• Explain why the mass of a reaction may decrease

  - Before the reaction, the reactants are contained in the reaction vessel

  
  

  - if the vessel isn't enclosed, then the gas produced can escape from the reaction vessel (as a gas will expand to fill any container it's in) so the mass decreases
• Give an example of a reaction where mass decreases

  Thermal decomposition of a metal carbonate producing a metal oxide and carbon dioxide gas
• When would a ionic compound end in 'ide'

  When there is ionic compound with 2 elements
• When would you use the ending 'ate'

  When an ionic compound contains 3 elements, 1 of them being oxygen
• What is the charge found in:

  Group 1

  Group 2

  Group 3

  Group 5

  Group 6

  Group 7

  Group 1 - 1+

  Group 2 - 2+

  Group 3 - 3+

  Group 5 - 3-

  Group 6 - 2-

  Group 7 - 1-
• What is the charge of:

  Fe(IV)

  Fe 4+
• What charge should you assume when the Roman neumarals on transition metals aren't stated?

  2+
• What are isotopes?


  An Atom of an element with the same number of protons but a different number of neutrons
• What is relative atomic mass(Ar)?

  The average mass of all stable isotopes of an element compared to an atom of carbon-12
• Define relative formula mass(Mr)

  The sum of the relative atomic masses of all the atoms shown in the formula.
• What is the mole

  The amount of a substance is measured in moles.

  1 mole is equal to the avogadro constant
• Define limiting reactant


  It is the reactant that is completely used up in a reaction.
• Which reactant would be the limiting reactant?

  The limiting reactant will be the reactant with the lowest moles after fractioning in the molar ratio
• How is uncertainty calculated?

  By doing a range, you never include anomalous results in any calculations
• What format is uncertainty shown in?


  Mean+uncertainty

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• Define solute


  Substance that dissolves in a liquid
• Define solvent


  liquid that dissolves the solute
• Define solution


  A mixture of a soluble solute that has been dissolved in a solvent
• Define saturated


  A solution in which the maximum amount of solute has been dissolved
• What is the formula for concentration

  concentration = mass of solute / volume of solution
• How would u work out relative atomic mass if 2 isotopes of Chlorine

  Ar(Cl) = (Isotope1 x (%of isotope1 / 100)) + (isotope2 x (%of isotope2 /100))
• What is the equation for working out moles

  Moles = mass / relative formula mass
• What are the units for this equation.

  Moles - mol

  Mass - g

  Relative formula mass - g/mol
• Describe the steps in calculating mass of reactions

  1 - calculate moles of known substance

  2 - use molar ration to find miles of unknown substance

  3 - calculate mass of unknown substance using moles
• What is the molar ratio the same as ?

  The balancing numbers
• 48g of magnesium reacts with 24g of oxygen to from magnesium oxide. Work out the limiting reactant and hence workout the mass of magnesium oxide

  
  

  Describe general steps on calculating limiting reactants

  1 - find moles of both oxygen and magnesium

  2 - factor in the molar ratio with both reactants to work out mass of mg0
• What is concentration measured in

  g/dm3
• What is mass of solute measured in

  Grams
• What is volume of solution measured in

  dm^3
• How many cm3 is 1dm3

  1000cm3
• How many ml is 1 cm3


  1
• How many dm3 in one l


  1
• How do u convert from cm3 to dm3

  / by 1000
• What is the formula for percentage yield

  percentage yield = mass of product made / maximum theoretical mass of product x 100
• Why might % yield be less than 100%

  - reaction may not go to completion

  - side reactions may produce unwanted products

  - some product may be lost during separation or warmup
• What is the formula for atom economy

  (Mass of desired product/total mass of products) x 100