C2b Flashcards
What is activation energy?
The minimum energy required in a collision for particles to react
What 4 factors affect the rate of a chemical reaction?
Temperature, pressure or concentration, surface area, catalysts
What is the experiment for the effect of temperature on rate of reaction? How does it work?
1) Sodium thiosulfate and HCl
Clear solutions make yellow precipitate
Time mark fading, repeat at different temperatures
2) Particles more faster - higher chance of collision, higher energy = more successful
What is the experiment for the effect of concentration on rate of reaction? How does it work?
1) Mg metal and HCl
H gas released - mass balance
Regular readings, repeat at different concentrations
2) Particles closer together, higher chance of collision
What is the experiment for the effect of surface area on rate of reaction? How does it work?
1) Marble chips + HCl
Gas syringe of CO2 at regular intervals
Repeat more crushed up
2) More particles available to react
What is the experiment for the effect of catalysts on rate of reaction? How does it work?
1) Decomposition of hydrogen peroxide
Measure O gas with syringe
Manganese IV oxide catalyst
2) Lowers Ea, provides surface for particles to stick to
What is a catalyst?
A substance that speeds up the reaction without being changed or used up
What are the advantages and disadvantages of using catalysts in a reaction?
+ Saves energy, environment, time, money
- Specific to reaction, expensive, can be poisoned
What is the equation for the rate of a reaction?
Rate = change in reactant / time
What are the three methods of measuring a reaction?
1) Precipitation - product clouds solution, time how long it takes for mark to disappear
2) Change in mass - gas given off
3) Volume of gas given off - with gas syringe in given time period
What is an exothermic reaction?
A reaction that transfers (heat) energy to the surroundings, usually shown by a rise in temperature e.g. combustion, neutralisation, oxidation - hand warmers
What is an endothermic reaction?
A reaction that takes in (heat) energy, usually shown by a fall in temperature e.g. thermal decomposition, sports injury packs
What is the equation for neutralisation?
Acid + base = salt + water
H+ + OH- = H2O
What is the difference between a base and an alkali?
Alkali = a base that can dissolve in water
What is the equation for an acid reacting with a metal?
Acid + metal = Salt + hydrogen
Why is the reactivity series relevant in a neutralisation reaction?
Any metal below H will not react
Are (hydr)oxides soluble or insoluble?
Insoluble
What is the equation for an acid reacting with a metal (hydr)oxide?
Acid + (hydr)oxide = Salt + water
What is the Haber process?
Rare neutralisation reaction as no water produced
Ammonia + Nitric acid = Ammonium nitrate
NH3 + HNO3 = NH4NO3
Which three salts are insoluble?
Lead Chloride (PbCl2) Silver Chloride (AgCl) Lead Sulfate (PbSO4)
What are the two ways to make soluble salts?
Using a metal or insoluble (hydr)oxide
Using an alkali
How do you make soluble salts using a metal or insoluble (hydr)oxide?
1) Excess metal to make sure all acid used up, stir
2) Filter excess
3) Evaporate
How do you make soluble salts using an alkali?
1) Add exact amount of alkali to neutralise acid using universal indicator
2) Repeat without UI
3) Evaporate water
How do you make an insoluble salt?
1) Pick solutions with ions you need
2) Once salt precipitated (lying at bottom), filter, wash ,dry
What can a precipitation reaction to make an insoluble salt be used for?
Remove unwanted ions from water - treat sewage
Ca and Mg removed to make water hard - stops soap lathering
What is electrolysis?
The splitting up of a substance with electricity
What carries electricity in electrolysis?
Electrolyte - liquid with free ions (when a salt is molten it will conduct electricity)
OIL RIG?
Oxidation is Loss
Reduction is Gain
What is the difference between a cation and an anion?
Cation = positive Anion = negative
What is the difference between a cathode and an anode?
Cathode = negative Anode = positive
Why is cryolite used in the electrolysis of aluminum oxide (bauxite ore)
To lower melting point from 2000 to 900 - save energy and money
Why is CO2 produced in the electrolysis of aluminum oxide?
Anode made from carbon so needs to be replaced
Why is the reactivity series important in electrolysis?
If both metal+ and H+ are present, metal will stay in solution as more reactive
What are halide ions?
Br, I, Cl - if these are present in a solution they will be formed. If not O2 is released
What is produced in the electrolysis of brine (NaCl solution)?
Cl2 gas
H2 gas
NaOH
What are Cl and NaOH used for?
Cl - bleach + plastics
NaOH - make soap
What are the half equations for the electrolysis of Al2O3?
Cathode: Al3+ + 3e- = Al
Anode: 2O2- - 4e- = O2
What is electroplating?
Coating the surface of an object with a metal
What needs to be in the electrolyte of any electroplating reaction?
Metal ions from the metal you want to coat an object with
What charges do the pure metal and object have in electroplating?
Pure metal - positive
Object - negative
Why do we use electroplating?
Decoration - cheaper to coat
Conduction
