C4

• What is the law of conservation of mass

  A law stating that no atoms are lost or made during a chemical reaction, the mass of the product equals the mass of the reactants
• What is relative formula mass?

  The sum of the atomic masses of all the atoms in a chemical formula/molecule.
• Why do some reactions appear to increase in mass?

  When substances react with gases in the air such as Oxygen, the mass will increase
• Why do some reactions appear to decrease in mass?

  When a gas is a product in a chemical reaction, it will release into the atmosphere
• How do you calculate uncertainty?

  Calculate the range in results and divide by 2
• What are Chemical amounts measured in?

  Moles
• What is the value of the Avogadro constant?

  6.02 x 10²³
• What is a limiting reagent?


  The reactant that is completely consumed in a chemical reaction and limits the amount of product that can be formed. (Limiting factor)
• What are the units for concentration?

  Mass per given volume
• Why is it not always possible to obtain the calculate amount of product?

  Equilibrium, the reaction is reversible

  Limitations, lost product during reaction
• What is yield?


  The amount of product obtained in a reaction
• What is atom economy?

  A measure of the efficiency of a chemical reaction, calculated by comparing the mass of desired product to the total mass of all reactants.
• Why is it important to use reactions with high atom economy?

  For sustainable development,

  It's cheaper.
• What is the unit for concentration?


  $Mol/dm^3$
• What is oxidation in terms of oxygen gain?

  Oxidation is when a substance gains oxygen.
• What is reduction in terms of oxygen loss?

  Reduction is when a substance loses oxygen.
• What is the reactivity series of metals and its trends?

  • Metals are ordered by reactivity.
  • Metals above H2 react with acids to produce H2.
  • More reactive metals react quicker and more violently with acids.
  • Metals below H2 do not react with acids.
  • Mostly Group I and II metals react with water; Aluminium is a borderline case.
• What is a displacement reaction?

  A displacement reaction is when a more reactive metal displaces a less reactive metal from a compound.
• How are unreactive metals found in Earth?

  Unreactive metals are found in their natural state.
• How can metals less reactive than carbon be extracted?

  They can be extracted by reduction with carbon.
• How are metals more reactive than carbon extracted?

  They are extracted by electrolysis.
• How are oxidation and reduction defined in terms of electron transfer?

  Oxidation is the loss of electrons, and reduction is the gain of electrons.
• What is the general equation for a reaction between metals and acids?

  Metal + acid → salt + hydrogen.
• What type of reaction occurs when metals react with acids?

  It is a redox reaction and also a displacement reaction.
• Which metals in the reactivity series will react with acid?

  Metals above hydrogen will react with acid.
• What is the general equation for a neutralisation reaction?

  Base + acid → salt + water.
• What is the general equation for the reaction between metal carbonate and acid?

  Metal carbonate + acid → salt + water + carbon dioxide.
• What is the general equation for the reaction between metal oxides and acids?

  Metal oxide + acid → salt + water.
• What is a redox reaction?

  A redox reaction is a reaction where both oxidation and reduction occur.
• In the reaction between magnesium and hydrochloric acid, which species is oxidised and which is reduced?

  Magnesium is oxidised (loses electrons), and hydrogen is reduced (gains electrons).
• How is a soluble salt formed?

  1. React excess acid with an insoluble chemical (e.g., metal oxide).
  2. Filter off the leftovers.
  3. Crystallise the product.
• What do acids produce in aqueous solutions?

  Acids produce hydrogen ions.
• What do alkalis produce in aqueous solutions?

  Alkalis produce hydroxide ions.
• What are bases, acids, and alkalis?

  • Bases neutralise acids.
  • Acids produce hydrogen ions in aqueous solutions.
  • Alkalis are soluble bases that produce hydroxide ions in aqueous solutions.
• What is the pH scale and what does a pH of 7 indicate?

  The pH scale measures acidity/alkalinity; a pH of 7 indicates a neutral solution.
• What is the short ionic form of the general equation for a neutralisation reaction?

  H+ + OH− → H2O.
• What is a strong acid?

  A strong acid is completely ionised in aqueous solution.
• What is a weak acid?

  A weak acid is only partially ionised in aqueous solution.
• What happens to pH as the concentration of H+ increases?

  The pH decreases as the concentration of H+ increases.
• What does a pH of 7 indicate about a solution?

  It indicates a neutral solution.