C3 Quantitative Chemistry

• Conservation of mass


  The law of conservation of mass states that no atoms are lost or made during a chemical reaction. Therefore: mass of the products = mass of the reactants
• Also Mr products = Mr reactants
• In an open system, the mass can change during an experiment involving gases


  • If a reactant is a gas, the mass increases (eg. 2 Ca + O2 → 2 CaO)
  • If a product is a gas, the mass decreases (eg. ZnCO3 → ZnO + CO2)
• Chemical formula


  Represents chemicals with symbols and numbers
• Atom


  The smallest particle of an element
• Element


  A type of atom found on the periodic table
• Mole


  Used to represent the number of particles. One mole is 6.02 x 1023 particles
• Limiting reactant


  The reactant that is completely used up during a reaction – this limits the amount of product
• Excess


  More of a chemical than you need for a reaction
• Mean


  The average of a set of numbers
• Range


  The highest minus the lowest number
• Uncertainty


  How close the highest and lowest numbers are to the mean
• Relative formula mass (Mr)


  The mass of one mole of a chemical in grams. It is found by adding the mass numbers of each atom in a chemical
• Masses and moles


  𝑚𝑜𝑙𝑒𝑠 = 𝑚𝑎𝑠𝑠/𝑀𝑟
• Concentrations of solutions


  The mass of the solute in 1 dm3 (1 litre) of solution
• Uncertainty in measurements


  Calculate the mean, range, and uncertainty
• Balanced chemical equations


  The 'balancing number' before each chemical shows the ratio of the number of moles of each chemical that reacts
• Mole ratios


  The mole ratios from a balanced chemical equation can be used to find the moles of one chemical from the moles of another
• Masses to balanced equations

  The mass can be used to find the mole ratio and write a balanced chemical equation
• Excess and limiting reactants


  The reactant which is used up is called the limiting reactant as this limits the amount of product formed in the reaction
• Finding the mass of one chemical from the mass of another (mole calculations!)

  1 - Find the moles, 2 - Use mole ratios, 3 - Answer the question
• The Wealth of Nations was written

  1776