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• write the chemical symbol of magnesium chloride

  • ionic compound
  • magnesium forms the ion Mg2+
  • chlorine forms the ion Cl-
  • chemical formula: MgCl2
• write the chemical symbol of zinc oxide

  • ionic compound
  • zinc forms the ion Zn2+
  • oxygen forms the ion O2-
  • chemical formula: ZnO
• write the chemical formula of phosphorus trichloride

  • covalent compound
  • phosphorus needs to gain three electrons to become stable so will form covalent bonds with three chlorine atoms
  • chemical formula: PCl3
• what is the balanced chemical equation for the reaction between hydrochloric acid and magnesium?

  Mg + 2HCl → MgCl2 + H2
• write the half equation for the formation of chloride ions from chlorine

  Cl2 + 2e- → 2Cl
• write the half equation for the formation of copper ions from copper

  Cu → Cu2+ + 2e
• what is the balanced chemical equation for the reaction between potassium bromide and chlorine?

  Cl2 + 2KBr → Br2 + 2KCl
• write the chemical formula of sulfuric acid

  • H2SO4
  • two H+ ions react with a sulfate ion (SO4 2-)
• what is an ionic equation?

  • an equations that only shows the ions which take part in a reaction
  • it can be written for any reaction involving ions in solution
• write an ionic equation for the reaction between nitric acid and sodium hydroxide?

  • HNO3 (aq) + NaOH(aq) → NaNO3 (aq) + H2O(l)

  rewrite the equation with the ions:

  • H + + NO3 - + Na+ + OH- → Na+ + NO3 - + H2O

  cancel any ions appearing on both side to get the ionic equation:

  • H + (aq) + OH- (aq) → H2O(l)
• write an ionic equation for the reaction between silver nitrate and sodium chloride?

  • AgNO3 (aq) + NaCl(aq) → AgCl(s) + NaNO3 (aq)

  rewrite the equation with ions:

  • Ag+ + NO3 - + Na+ + Cl- → AgCl + Na+ + NO3 -

  cancel any ions appearing on both side to get the ionic equation:

  • Ag+ (aq) + Cl- (aq) → AgCl(s)
• what do the 4 state symbols mean?

  (s) - solid

  (l) - liquid

  (g) - gas

  (aq) - aqueous/ dissolved in water
• write the chemical equation for the reaction between calcium carbonate and hydrochloric acid. include state symbols

  CaCO3 (s) + 2HCl(aq) → CaCl2 (aq) + H2O(l) + CO2 (g)
• mole


  one mole is the amount of a substance containing the same number of particles as there are atoms in exactly 12.0 g of carbon-12. this is 6.02 x 10^23 particles
• what is the Avogadro constant?

  the number of atoms, molecules or ions in one mole of a given substance. this has a value of 6.02 x 10^23
• what equation links the Avogadro constant to number of moles?

  number of particles = moles x Avogadro constant
• how many atoms are there in 0.622 moles of calcium?

  • number of atoms = moles x Avogadro’s constant
  • = 0.622 x (6.02 x 1023)
  • = 3.74 x 10^23 atoms
• what is equal to the mass of one mole of a substance?

  relative atomic mass
• what equation links mass, number of moles and relative atomic mass?

  mass (g) = moles x relative atomic mass (Mr)
• how many moles are there in 6.25 g of aluminium?

  • moles = mass ÷ relative atomic mass
  • = 6.25 ÷ 27
  • = 0.231 (3.s.f)
• how many atoms are there in 0.375 g of sodium?

  • moles = 0.375 ÷ 23
  • = 0.0163 moles
  • number of atoms = 0.0163 x (6.02 x 10^23) = 9.82 x 10^21
• what is the law of conservation of mass?

  • no atoms are lost or gained during a chemical reaction
  • mass of products equals mass of reactants
• the law of conservation of mass states that the mass of reactants equals the mass of products

  why might you record a decrease in mass during an reaction? 


  if a gaseous product is formed in a non-enclosed system, the gas will escape the reaction vessel and won’t be included in the mass
• what is a limiting reagent?

  • in a reaction between two substances, one reactants will often be used in excess to ensure that all of the other reactant is used up
  • the reactant which isn’t in excess is the limiting reagent as it limits the amount of product that can be formed
• how can you balance an equation if you are given the mass of the reactants and products?

  • use the mass quantities to calculate the number of moles of the reactants and products
  • divide the number of mole of each substance by the smallest number to give the simplest ratio of the compounds
  • this gives the numbers for the balanced equation
• 127 g of copper reacts exactly with 32 g of oxygen. using the masses, what is the balanced equation?

  • 159 g of CuO is formed since mass of reactants = mass of products.
  • number of moles of oxygen = 1
  • number of moles of copper = 2
  • number of moles of copper oxide = 2
  • ratio Cu:O2 :CuO is 2:1:2 so the balanced equation is:
  • 2Cu + O2 → 2CuO
• endothermic

  the reaction take in energy so the temperature of the surroundings decreases
• exothermic

  the reaction releases energy so the temperature of the surroundings increases
• give two examples of an exothermic reaction

  • combustion
  • neutralisation
• give two examples of an endothermic reaction

  • thermal decomposition
  • photosynthesis
• what is a reaction profile?

  a graph that shows the activation energy of a reaction with the relative energies of the reactants and products
• reaction profile for an endothermic reaction

  A) energy

  B) reactants

  C) higher

  D) products

  E) reaction

  F) positive

  
• reaction profile for an exothermic reaction

  A) negative

  B) lower

  C) products

  D) energy

  E) reactants

  F) reaction

  
• what is needed for a reaction to occur?

  reactant particles need to collide at the correct orientation with sufficient energy
• what is the activation energy of a reaction?

  the minimum energy required for a reaction to occur
• in terms of bond energies, what happens in a chemical reaction? describe exothermic and endothermic reactions in terms of bonds breaking/ forming

  • energy is needed to break bonds. energy is released when making bonds
  • exothermic: energy used to break bonds is greater than the energy released when making bonds
  • endothermic: energy released when forming bonds is greater than the energy used to break bonds
• How can the energy change of a reaction be calculated using bond energies? (Higher only) Energy of reaction = total energy of bonds broken - total energy of bonds made
• how can the energy change of a reaction be calculated using bond energies?

  energy of reaction = total energy of bonds broken - total energy of bonds made
• describe reduction and oxidation in terms of oxygen

  • reduction: loss of oxygen atoms
  • oxidation: gain of oxygen atoms
• describe reduction and oxidation in terms of electrons

  • reduction: gain of electrons
  • oxidation: loss of electrons