Rate of reaction & redox

Question 1

How to measure speed of reaction (3)

Answer 1

• volume of gas produced per unit time
• mass of reactant used up per unit time
• rate of effervescence

Question 2

How does reaction occur between 2 particles (3)

Answer 2

• reacting particles must collide with each other
• collide with minimum amount of energy known as activation energy
• collision of products must be EFFECTIVE to form product

Question 3

Concentration of the reactants (factors affecting ROR) (4)

Answer 3

• increase concentration of sol
• more reacting particles occupying given vol
• increase in frequency of effective collision between reactant particles
• ROR increase with higher conc

Question 4

Pressure of gaseous reactants (factors affecting ROR) (4)

Answer 4

• increase pressure
• decrease volume between reactant gas molecules
• increase in frequency of effective collision between reactant particles
• increased pressure increases ROR

Question 5

Particle size or surface area of particles (factors affecting ROR) (4)

Answer 5

• decrease particle size or using powdered reactant
• increased SA of reactants exposed for reaction
• increase in frequency of effective collision between reactant particles
• ROR increases

Question 6

Increasing temp (factors affecting ROR) (5)

Answer 6

• increase temp of sol
• reactant particles have more energy, more particles have energy greater than activation energy
• particles move faster with greater energy
• higher frequency of effecting collision
• ROR increase

Question 7

Catalyst (factors affecting ROR) (4)

Answer 7

• presence of catalyst
• lowers activation energy for products to be formed
• lesser amount of energy required for effective collision
• ROR increase

Question 8

Catalysts examples (2)

Answer 8

• Aluminium oxide or silver oxide in cracking organic compounds to form H2 gas
• Nickel in hydrogenation of Alkenes to Alkanes

Question 9

How to determine redox (4)

Answer 9

• in terms of oxygen (oxi - gain O)
• in terms of hydrogen (oxi - lose H)
• in terms of electrons (oxi - lose e)
• in terms of oxidation state (oxi - increase OS)

Question 10

What reactions are non redox? (2)

Answer 10

• neutralisation
• ionic precipitation

Question 11

Oxidising agent examples (8)

Answer 11

• Bromine (Br2)
• Chlorine (Cl2)
• Oxygen (O2)
• Hydrogen peroxide (H2O2)
• Potassium manganate(VII) (KMnO4)→purple turns colourless if RA present
• Potassium dichromate(VI) (K2Cr2O7)→ orange turns green if RA present
• Concentrated sulfuric acid (H2SO4)
• Nitric acid (HNO3)

Question 12

Reducing agents examples (8)

Answer 12

• Metals
• Carbon (C)
• Carbon monoxide (CO)
• Hydrogen (H2)
• Hydrogen sulfide (H2S)
• Sulfur dioxide (SO2)
• Ammonia (NH3)
• Potassium iodide (KI) →colorless turns brown if OA present

Question 13

Exothermic reaction examples (6)

Answer 13

• Combustion
• Neutralisation
• Extraction of iron in the Blast Furnace
• Corrosion of metals (e.g. rusting of
  iron)
• Respiration
• Condensation

Question 14

Endothermic reaction examples (5)

Answer 14

• Dissolving some ionic compounds (e.g. ammonium chloride, sodium carbonate crystals) in water
• Thermal decomposition CaCO3 heat CaO + CO2
• Photosynthesis - chlorophyll and other plant pigments absorb energy (light) from the Sun to convert carbon dioxide and water into glucose and oxygen.
• Action of light on silver bromide in photographic film
• Evaporation

Question 15

Bond breaking (energy changes in chemical rXn) (2)

Answer 15

• energy is required to break bonds
• endothermic

Question 16

Bond making (energy changes in chemical rXn) (2)

Answer 16

• energy released when bonds formed
• exothermic