6152554
Descripción
Fichas por Mel Hughes, actualizado hace más de 1 año
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Creado por Mel Hughes
hace más de 8 años
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| Pregunta | Respuesta |
| What two types of measurement must be made to find the average rate of a reaction? | Amount (of reactant or product) and time |
| How can we use a graph of amount of product against time to tell us the rate of the reaction at a given time? | The gradient of the line at a given time gives the rate at that time |
| What do we call the minimum energy needed for the particles to react? | Activation energy |
| List the factors that increase the rate of a reaction | Increasing: temperature, concentration of solutions, pressure of gases, surface area of solids; using a catalyst |
| Why do powders react faster than large pieces of solid? | Powders have a greater surface area than large lumps of solid, and this increases the chance of collisions |
| Why does a small change in temperature have a large effect on the rate of reaction? | It increases the frequency of collisions and the energy of the particles |
| Why do reactions in solutions go faster at higher concentrations? | It increases the frequency of collisions |
| Why does increasing the pressure increase the rate of a reaction of two gases? | The frequency of collisions increases because there are molecules in the same volume |
| Why can catalysts be used over and over again? | They remain at the end of a reaction or they are not used up in the reaction |
| Why do different reactions need different catalysts? | Catalysts often work with only one type of reaction |
| What are the benefits of using catalysts in industrial processes? | They reduce the energy needed and the time needed, and so reduce costs. They may reduce the amount of fossil fuel used and so conserve resources and reduce pollution |
| Give one disadvantage of transition metal catalysts | They may be toxic or expensive |
| What two areas of research offer possibilities for new or better catalysts? | Nano science and enzymes |
| How can you tell that burning natural gas is an exothermic reaction? | It transfers energy energy to the surroundings or heats the surroundings |
| What are the two ways that show that a reaction is endothermic? | Either it cools the surroundings or it needs to be heated to keep it going |
| Why must blue copper sulphate be heated continuously to change it into anhydrous copper sulfate? | It is an endothermic reaction |
| Why does adding water to anhydrous copper sulfate cause the mixture to get hot? | It is an exothermic reaction |
| Suggest one advantage of a re-usable hand warmer compared with a single use hand warmer | One advantage e.g. -Less waste - Less materials/resources used |
| Suggest one disadvantage of a re-usable hand warmer compared with a single use hand warmer | One disadvantage e.g. - Has to be heated or needs energy so it can be used again - Slower reaction - Smaller temperature rise. |
| Suggest one advantage of a chemical cold pack compared with using an ice pack | One advantage e.g. -Can be used anywhere - Can be stored easily (ice needs to be made and/or stored in special equipment) |
| Suggest one disadvantage of a chemical cold pack compared with using an ice pack | One disadvantage e.g. - Can only be used once - More waste -Possibly more hazardous than ice |
| Pieces of zinc react with dilute hydrochloric acid Zn(s) + 2HCl(aq) -> ZnCl2(aq)+H2(g) In what ways could you increase the rate of the reaction between zinc and hydrochloric acid? | Increase concentration of acid, increase temperature, use powdered zinc, use a catalyst |
| How can you find the rate of a reaction from a graph of mass of product against time? | From the gradient or slope of the line |
| What is meant by the 'activation energy' of a reaction? | The minimum energy that particles must have for collisions to produce a reaction |
| Name two types of reaction that are exothermic | Two examples; e.g. - Combustion - Oxidation -Neutralisation |
| Why must calcium carbonate be heated continuously to convert it into calcium oxide and carbon dioxide? | (Thermal decomposition is) an endothermic reaction |
| Nitrogen and oxygen react together to produce nitrogen oxide: N2(g) + O2(g) ->2NO(g) What changes in conditions would increase the rate of this reaction? | High temperature, high pressure, catalyst |
| Explain in terms of particles why increasing the concentration of a reactant increases the rate of the reaction | Particles are closer together (more particles in the same volume), so collisions are more frequent (more collisions per second) |
| Explain why increasing the temperature increases the rate of a reaction | Particles collide more frequently, and with more energy so more collisions have the activation energy (minimum energy needed for reaction) |
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