C6 Flashcards
What does the pH scale show?
It shows how acidic or alkaline a solution is
- An acid has a pH less than 6
- An alkali has a pH more than 8
- pH 7 is neutral
What do acids produce in water?
They produce hydrogen atoms, H+
When the concentration of H+ ions increases by 10, what happens to the pH level?
Decreases by 1
What makes an acid a ‘strong’ acid?
Strong acids ionise completely in water
What makes an acid a ‘weak’ acid?
Weak acids do not fully ionise in water.
What does an acid and a metal hydroxide form?
Salt + Water
What does an acid and a metal form?
Salt + Hydrogen
What does an acid and a metal carbonate form?
Salt + Water + Carbon Dioxide
How can you make a soluble salt?
Reacting an acid with an alkali.
How can you make an insoluble salt using precipitation?
Reacting 2 soluble salts which produce a precipitate
-e.g. to make lead chloride you mix lead nitrate and sodium chloride which are both soluble
What is the rate of reaction?
How fast the reaction happens
What is the collision theory?
- How often particles collide
- The more frequent the collisions are, the faster the reaction rate is.
- Particles must collide with enough energy for the reaction to take place.
- The more successful collisions, the higher the rate of reaction.
What effect does increasing the temperature have on the rate?
- Particles move faster and have more frequent collisions
- Higher temperatures increase the energy in the reaction, so reactions will be more successful
- Therefore increasing the temperature will increase the rate.
What effect does increasing the concentration/pressure have on the rate?
-There are more particles in the same volume, so collisions are more likely, so the reaction rate increases.
What effect does increasing the surface area have on the rate?
-Particles have more area to react upon (collisions only occur on the surface) so collisions are more likely, so the rate increases.
What effect does a catalyst have upon the rate?
Speeds up reaction by lowering activation energy, but has no effect on the yield
-it is not part of the overall equation
What effect do enzymes have upon the reaction?
If the temperature is too high or low, the enzyme will not work at a high rate-the temperature has to be specific for the enzyme to work at an optimum rate.
What is the equation for rate of reaction?
Amount of product formed / time
What are reversible reactions?
Reactions which can go forwards and backwards
-can reach an equilibrium where the forwards and backward reactions slow down.
What are the 3 factorss which can affect the position of the equilibrium?
- Temperature
- Pressure
- Concentration
How does temperature affect the position of the equilibrium?
If you increase the temperature, the equilibrium will shift towards the endothermic side.
How does the pressure affect the position of the equilibrium?
If you increase the pressure, the equilibrium shifts to the side with fewer particles
How does concentration affect the position of the equilibrium?
If you increase the concentration of the reactants, the equilibrium will shift to the products side.
What is atom economy?
The % of reactants forming desired products.
What is the equation for atom economy?
Mass of desired products / mass of all reactants
What are the benefits of high atom economy?
- Little waste
- More profitable
- Waste products can be expensive to remove.
What factors do industrial processes have to take into account?
- Cost of raw materials
- Yield
- Rate
- Position of equilibrium
What is yield?
The amount of product formed.
What decisions do industries have to make on raw materials?
- How much energy used
- How much waste produced.
- The atom economy.
What decisions do industries have to make on energy?
- How much energy is produced from non-renewable resources
- How much energy is required
What decisions do industries have to make on products?
- How much desired products are formed
- How much waste products are formed
What is the formula for the Haber Process?
Nitrogen+Hydrogen> Ammonia
What happens in the Haber Process?
- Nitrogen and hydrogen obtained
- Reactant gases passed through an iron catalyst at a temperature of 450 and a high pressure of 200 atmospheres
- reaction is reversible so some ammonia converts back to nitrogen and hydrogen
- unused reactants react again
What are the uses of fertilisers?
Replace missing elements in soil, which helps increase the crop yield, as it causes plants to grow faster and stronger.
What are the positives of fertilisers?
-Allows more food to be produced
What is eutrophication?
- Fertilisers run off into rivers and lakes
- Level of nitrates and phosphates increases in water
- Algae and weeds multiply rapidly, which blocks light to plants below, so they can’t photosynthesise and die.
- Aerobic bacteria begin to use up all the oxygen to survive, so everything in thee water dies.
How can fertilisers made from ammonia?
Ammonia can be neutralised with acids to form fertilisers.
-Fertilisers are produced on a large, bulk scale.
