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SC14 + SC15 part 1

Pearson GCSE Chemistry

QuestionAnswer
What is the actual yield of a chemical reaction? The actual amount of product obtained from a chemical reaction.
What is the theoretical yield of a chemical reaction? The maximum calculated amount of a product that could be formed from a given amount of reactants.
What is the percentage yield of a chemical reaction? The actual yield divided by the theoretical yield, as a percentage.
List the three reasons why percentage yields are less than 100% Incomplete Reaction, Side Reactions, Some of the product lost either in transfer from one container to another or left behind in a container.
What is a side reaction? A reaction which takes place at the same time as another main reaction.
What is the atom economy of a chemical reaction? The percentage, by mass, of reactants that are converted into useful products.
What is a by-product? Any product formed in a reaction in addition to the required product.
What is the formula for concentration of a solution in g dm-3 concentration in gdm-3 =mass(g)/Volume(dm3)
What is the name for the flask which is accurately calibrated to measure a given volume of solution? A volumetric flask
What is the formula for concentration of a solution in mol dm-3 ? concentration in moles dm-3 = moles/volume(dm3)
What is the formula that links the two types of concentration? concentration in moles dm-3= concentration in gdm-3/ Relative Formula Mass
What is the Haber process? A reversible reaction between nitrogen and hydrogen forming ammonia
In an industrial reaction why would you carry it out at a high temperature even if this would shift the equilibrium to the left hand side and reduce percentage yield? To increase the rate of the reaction, saving time
What elements do fertilisers contain? Nitrogen, phosphorus and potassium (NPK)
What are fertilisers used for? To promote plant growth
What is formed when ammonia reacts with nitric acid? Ammonium nitrate
Why is ammonium nitrate a good fertiliser? NH4NO3, contains 2 nitrogen atoms per molecule
How would you make ammonium sulphate? From ammonia and sulfuric acid
How will an increase in temperature affect the rate of attainment of equilibrium? Equilibrium wil be reached quicker.
How will an decrease in temperature affect the rate of attainment of equilibrium? Equilibrium wil be reached slower.
How will an increase in pressure affect the rate of attainment of equilibrium? Equilibrium wil be reached quicker.
How will an decrease in pressure affect the rate of attainment of equilibrium? Equilibrium wil be reached slower.
How will an increase in concentration affect the rate of attainment of equilibrium? Equilibrium wil be reached quicker.
How will an decrease in concentration affect the rate of attainment of equilibrium? Equilibrium wil be reached slower.
How will adding a catalyst affect the rate of attainment of equilibrium? Equilibrium wil be reached quicker.
Why would you choose a lower/medium pressure when a high pressure would give a better yield? To reduce costs and risk.
Why would you choose a high temperature when a low temperatuer would give a better yield? To increase rate of reaction
Why would you use a catalyst in an industrial reaction? To increase rate of reaction and reduce costs.
Write a word equation for the reaction of ammonia and nitric acid. ammonia + nitric acid --> ammonium nitrate
Why does increasing temperature increase rate at which equilibrium is reached? There are more frequent collisions between particles so the rate of reaction increases.
Why does increasing pressure increase rate at which equilibrium is reached? There are more frequent collisions between particles so the rate of reaction increases.
What is being described here: is a piece of equipment used to accurately measure and transport a measured volume of liquid, A pipette
What piece of equipment is being described here: a graduated glass tube with a tap at one end, for delivering known volumes of a liquid, especially in titrations A burette.
What is titration? The slow addition of one solution of a known concentration to a known volume of another solution of unknown concentration until the reaction is complete.
When are titre values said to be concordant? When they are within 0.2cm3 of each other.
State Avogadro’s law If the temperature and pressure are the same, equal volumes of different gases contain an equal number of molecules.
What is the molar volume of a gas? The volume occupied by one mole of a gas at a certain temperature.
Describe the difference between a batch process and a continuous process. In a continuous process substances are made constantly in a batch process substances are made in separate stages.
What is the Haber Process? A reversible reaction between nitrogen and hydrogen which forms ammonia.
Write the chemical reaction for the formation of ammonium nitrate from nitric acid and ammonia NH3 + HNO3 à NH4NO3
Write the chemical reaction for the formation of ammonium sulfate from sulfuric acid and ammonia 2NH3 + H2SO4 à (NH4 )2SO4