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SC14H SC15H part 1
Pearson GCSE Chemistry
| Question | Answer |
|---|---|
| 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 |
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Davenant Foundation School
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