Chemical changes

• what’s oxidation?

  When a substance gains oxygen. It loses electrons.
• whats reduction?

  When a substance loses oxygen and gains electrons.
• What’s the reactivity series?

  A list of metals in order of their reactivity.
• What are the trends in the reactivity of metals in reactions with acid/water?

  Metals above hydrogen in the reactivity series react with acid to produce hydrogen. The more reactive the metal is the quicker and more violent the reaction that occurs is. Metals below hydrogen don’t react with acids. Not all metals above hydrogen react with water mostly group 1/2 metals or aluminium.
• What is a displacement reaction?

  A chemical reaction where one less reactive metal is replaced by another more reactive metal in a compound.
• How are unreactive metals found in earth?

  In their natural state.
• How can metals less reactive than carbon be extracted?

  Reduction with carbon. Carbon displaces the metal in a metal oxide - gets oxidised to carbons oxides. Metal from the metal oxide gets reduced to the pure metal.
• How are metals more reactive than carbon extracted?

  Electrolysis.
• What’s the general equation for a reaction between metaks and acids? What type of reaction is this?

  Metal + Acid —> salt + hydrogen

  This is both a displacement and redox reaction.
• What metals in the reactivity series react with acid?

  Any above hydrogen.
• What’s the general equation for a neutralisation reaction?

  Acid + Base -> Salt + Water
• What’s the general equation for the reaction between metal carbonate and acid?

  Metal carbonate + acid → salt + water + carbon dioxide
• What’s the general word equation for the reactions between metal oxides and acids?

  Metal oxide + acid -> salt + water
• What’s a redox reaction?

  A reaction where both oxidation and reduction occur.
• How is a soluble salt formed?

  react the excess acid with some insoluble chemical (metal oxide). Filter off the leftovers. Crystallise product.
• what do acids and alkalis produce in aqueous solutions?

  Acids produce hydrogen ions, alkalis produce hydroxide ions.
• What are bases?

  Bases are compounds that neutralise acids.
• What are acids?

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

  Alkalis are a soluble base that produces hydroxide ions in aqueous solutions.
• What’s the pH scale?

  The measure of acidity/alkalinity of a solution.
• What does 7 show on the pH scale?

  Neutral solution.
• State the general equation for neutralisation reaction in a short, ionic form.

  H(+) + OH(-) —> H2O
• Whats a strong and weak acid?

  Strong acid: Completely ionised in aqueous solutions. Weak acid: Partially ionised in aqueous solutions.
• What happens to the pH as the concentration of H+ increases?

  pH decreases.
• What is a concentrated acid?

  Concentrated acids have more moles of acid per unit volume than dialute.
• What’s a diluted acid?

  A dilute acid have less moles of acid per unit volume.
• Are concentrated and dilute acids the same as strong and weak acids?

  No, concentration ≠ strength. Strength refers to how ionised the acid is in water concentration refers to moles of acid per unit volume.
• As the pH decreases by one unit what is the change seen in the hydrogen ion concentration?

  Increases by a factor of 10.
• Write the salt LITHIUM NITRATE in its molecular formula.

  LiNO3
• Write the salt POTASSIUM CARBONATE as its molecular formula.

  K2CO3
• Write the salt MAGNESIUM BROMIDE as its molecular formula.

  MgBr2
• Write the salt BARIUJ SULFATE as its molecular formula.

  BaSO4
• Define electrolysis.

  The passing of an electric current through ionic substance (molten or in aqueous) to break them down into elements; ions are discharged (they lose/gain electrons) at electrodes to produce these elements.
• What’s an electrolyte?

  the liquid / solution which conducts electricity.
• What’s the cathode?

  Negative electrode.
• What’s the anode?

  Positive electrode.
• during electrolysis, what occurs at the cathode?

  Reduction.
• During electrolysis, what occurs at the anode?

  Oxidation.
• In aqueous electrolysis, which elements is discharged at the cathode and anode?

  At the cathode the less reactive element discharged at the cathode. Hydrogen is produced unless there is a less reactive metal in which case the metal is produced.

  Oxygen is produced at the anode unless the solution contains halide ions in which case halogen molecules are produce.
• How is aluminium manufactured and why is it expensive?

  Electrolysis of aluminium oxide and cryolite which is energy-intensive.