C2b Flashcards
What 4 things does rate of reaction depend on?
Temperature, concentration/pressure, catalyst, surface area (solids)
What are the 2 ways rate of reaction can be measured?
How quickly reactants are used up
How quickly the products are formed
What is the formula for rate of reaction?
Amount of reactant used/product formed ÷ time
What 3 things can rate of reaction be measured by?
- Precipitation- cloudy solution- cross under flask
- Change in mass- gas given off- mass balance
- Volume of gas given off- gas syringe
What are the 3 rate of reaction experiments and what do they measure?
- Hydrochloric acid and marble chips- gas given off
- Reaction of magnesium metal with hydrochloric acid- change in mass
- Sodium thiosulfate and hydrochloric acid- precipitation
What is the collision theory?
The more collisions in particles = the faster the rate of reaction
What 3 things increase collisions and why?
- Higher temperature- more kinetic energy so particles move quicker
- Higher concentration/pressure- more particles of reactant knocking water particles/pressure means particles are squashed together
- Larger surface area- particles around it in solution will have more area to work on
Reactions can only happen if…
particles collide with enough energy
What’s a catalyst?
A substance that speeds up the rate of reaction without changing it or being used up in the reaction
How does a solid catalyst work?
It gives the reacting particles something to stick to, increasing the number of successful collisions
How do catalysts reduce costs in industrial reactions?
They increase the rate of reaction- this saves money because plants and machines don’t need to operate for as long. The reaction can operate at a lower temperature which reduces energy needed- saves money/sustainable
What are the disadvantages of using catalysts in the industry?
- Expensive to buy
- Need to be removed from product and cleaned
- Different reactions need different catalysts
- Can sometimes be poisoned by impurities so they stop working
What’s an exothermic reaction?
One which transfers energy to the surroundings, usually in the form of heat and is shown by a rise in temperature
What’s an example of an exothermic reaction?
Burning fuels (combustion)
What everyday items use exothermic reactions?
Handwarmers/self heating cans
What’s an endothermic reaction?
One which takes energy from the surroundings (in the form of heat) and is shown by a fall in temperature
What’s an example of an endothermic reaction?
Thermal decompositions
What everyday items use endothermic reactions?
Sports injury ice packs
In a reversible reaction, if a reaction is endothermic in one direction, it will be…
exothermic in the other direction
What is the pH scale and what does it go up to?
A scale used to measure how acidic or alkaline a solution is, it goes from 0-14
Which side of the pH scale is acidic?
0-6
Which number on the pH scale is neutral?
7
WHich side of the pH scale is alkaline?
8-14
What is indicator?
A dye that changes colour depending on whether it’s above or below a certain pH
What’s a base?
A substance with a pH greater than 7- and alkali is a base that dissolves in water
What type of ions do alkalis form?
OH-
What type of ions do acids form?
H+
What’s the word equation for neutralisiation?
acid + base = salt + water
What’s the word equation for acids reacting with metals?
Acid + metal = salt + hydrogen
The more reactive the metal, the faster the reaction, true or false?
True
When metals react with acids, what’s the speed of reaction indicated by?
The rate at which bubbles are given off
How is hydrogen confirmed in a reaction?
The burning splint test- squeaky pop
Which salts will hydrochloric acid produce?
Chloride salts
Which salts will sulfuric acid produce?
Sulfate salts
What are metal oxides and metal hydroxides?
Bases
All metal oxides and hydroxides react with acids to form…
salt and water
What does hydrochloric acid + copper oxide make?
Copper chloride and water
What does sulfuric acid + zinc sulfate make?
Zinc sulfate and water
What does nitric acid + magnesium oxide make?
Maagnesium nitrate and water
What neutralises ammonia to make fertiliser?
HNO3
Briefly describe the steps to make soluble salts using a metal or insoluble base:
- Pick the right acid plus a metal of insoluble base
- Add to the acid and wait for the solid to dissolve as it reacts
- Filter out the excess metal to get the salt solution
- Evaporate some of the water and leave the rest to exaporate slowly- crystalisation
Briefly describe the steps to make soluble salts using an alkali:
- Add exactly the right amount of alkali to neutralise the acid (using indicator first, then without)
- Then evaporate off the water to crystalise the salt
Briefly describe the steps of making insoluble salts using a precipitation reaction:
- You need 2 solutions with the ions you need
- Once the salt has precipitated out, filter it from the solution
- Wash&dry it on filter paper
What does electrolysis mean?
Splitting up with electrons
Briefly describe the process of electrolysis:
- An electric current through an ionic substance that’s molten or in solution, it breaks down into the element it’s made from
- Requires a liquid to conduct the electricity- electrolyte
- Electrolytes contain free ions that conduct electricity
- Electrons are taken away from ions at the positive electrode and given to other ions at the negative electrode
Electrolysis always involves oxidation and reduction- what are these?
Oxidation: Loss of electrons (gain of oxygen) OIL
Reduction: The gain of electrons RIG
What do half-equations show?
The reactions at the electrodes
How is aluminium extracted from its ore?
Using electrolysis
What’s the process of removing aluminium from its ore?
- Aluminium oxide is dissolved in molten cryolite (metling point brought down to 900 degrees)
- Aluminium forms at the negative electrode and oxygen forms at the positive one
What is electroplating?
When electrolysis is used to coat the surface of one metal with another metal
In electroplating what is the negative electrode and what is the positive electrode?
Negative: Object you want to plate
Positive: The pure metal you want it to be plated with
What are the uses for electroplating?
Decoration and conduction
