CHAPTER 12: REDOX REACTIONS

Question 1

what are redox reactions

Answer 1

• reduction and oxidation
• oxidation is defined as the loss of electrons
• reduction is defined as the gain of electrons
• eg. - 2Mg(s) + O2(g) → 2MgO(s)
  
  • oxidation: Mg(s) → Mg2+(s) + 2e-
  • reduction: O2(g) + 4e- → 2O2-(aq)

Question 2

oxidising agent/oxidant

Answer 2

• causes another chemical to be oxidised
• in the reaction, they are reduced
• accepts electrons

Question 3

reducing agent/reductant

Answer 3

• causes another chemical to be reduced
• in the reaction they are oxidised
• loses electrons

Question 4

conjugate redox pairs

Answer 4

an oxidising agent and its corresponding reducing agent are known as a conjugate redox pair

Question 4

metal displacement reactions

Answer 4

• the order in which metals and their ions appear in the reactivity series enables you to predict which metals will displace other metals from solutions of their ions
• a metal ion higher in the reactivity series (oxidising agent) will react with a metal lower in the reactivity series (**reducing **agent)
  
  • top left and bottom right are the reactants

Question 5

spontaneous redox reactions

Answer 5

example 1: predict whether zinc will displace copper from a solution containing copper (II) ions and write the overall equation for the reaction

• copper is on top of zinc
• reduction: Cu2+ (aq) + 2e- → Cu(s)
• oxidation: Zn(s) → Zn2+(aq) + 2e-
• overall equation Zn(s) + Cu2+ (aq) → Zn2+(aq) + Cu(s)

the metal ion is above the metal ion of the other metal for a spontaneous redox reaction to occur

Question 6

simple galvanic cell

Answer 6

• salt bridge → filter paper soaked in KNO3
• each half-cell contains:
  
  • electrode
  • electrolyte
• in a galvanic cell, the strongest reducing agent will be oxidised and, if it is a metal, it will be the negative electrode.
• ANODE - OXIDATION (ANOX)
  
  • oxidation occurs at the anode
• REDUCTION - CATHODE (REDCAT)
  
  • reduction occurs at the cathode
  • oxidation occurs on the leftm reduction on the right

Question 7

purpose of salt bridge

Answer 7

completes the circuit by allowing ions to move from one half-cell to the other

Question 8

what is a battery

Answer 8

• can be a single-cell or multiple cells
• based on a simple galvanic cell
• primary cell
  
  • a cell that is disposable and designed not to be recharged
• dry cell: electrolyte is acidic
• alkaline cell: electrolyte is alkaline
• secondary cell
  
  • rechargeable cell that is designed to be reused many times
  • are useful bc they ar lightweight, portable source of electricity and used in wireless devices