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Description
Flashcards by Czean Holgado, updated more than 1 year ago
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Created by Czean Holgado
about 7 years ago
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| Question | Answer |
| What is chemical synthesis? | Chemical synthesis means using simple substances to make new, useful chemical compounds. |
| State 6 main chemicals that are produced from chemical synthesis. | •Food additives •Fertilisers •Dye stuffs •paints •pigments •pharmaceuticals |
| Indicators turn different colours in acids and alkalis. What colour is litmus paper/universal indicator in acids and alkalis? | •Litmus is red in acids and blue in alkalis •Universal indicator is orange or red in acids and green to blue in alkalis. |
| Pure acids compounds can or solids, liquids, or gases. Give examples of acids that are solid, liquid, or gas when pure. | Solids - citric acid; tartaric acid Liquid - sulfuric acid; nitric acid; ethanoic acid Gas - hydrochloric acid |
| What is pH a measure of? | The pH scale is a measure of how strong an acid or an alkali is. |
| On the pH meter, how can you tell whether a substance is neutral, acidic or alkaline? | •Neutral solutions have a pH of 7. •Acids have a pH number below 7. •Alkalis have a pH number above 7. |
| What do acids react with to form a salt? | Acids react with many metals and metal compounds to make a salt. |
| What else is usually formed apart from a salt when a metal reacts with an acid? | Acids react with metals to form a salt and HYDROGEN gas. |
| What is the word equation for the reaction of calcium and hydrochloric acid? | Calcium + hydrochloric acid --> calcium chloride + hydrogen. |
| What is formed when an acid reacts with metal oxides and hydroxides? | •a metal salt and water |
| Salts are ionic compounds. What does this mean? | It contains a positively charged metal ion and a negative ion from the acid. |
| What is formed when acids react with metal carbonates? | •It forms a salt, carbon dioxide, and water. |
| What is the name for the reaction that occurs when an acid and an alkali react? | When an acid reacts with an alkali, it becomes neutral - this is called a neutralisation reaction. |
| What is a titration used for? | A titration is used to measure the volume of acid and alkali that exactly react together. |
| Why are outliers left out when you calculate the mean? | •They are usually the result of errors in measurement. |
| What is always formed when an acid and an alkali react? | •Salt and water are produced. |
| What do all acids contain when dissolved in water? | •Positively charged hydrogen ions (H+) |
| What do all alkalis contain when dissolved in water? | •They all contain negatively charged hydroxide ions (OH-) |
| What are exothermic reactions? | Exothermic reactions give out heat energy. The temperature of the surroundings rises. |
| What are endothermic reactions? | Endothermic reactions take in heat energy. The temperature of the surroundings fall. |
| What changes as an exothermic reaction occurs, in terms of the energy of the reactants and the products? | •As exothermic reactions give out energy, the reactants will always have a higher energy value than the products. |
| What changes as an endothermic reaction takes place, in terms of the energy of the reactants and the products? | •The reactants take in energy, so the products will always have a higher energy value than the reactants. |
| What is a pure substance? | A pure substance has nothing else mixed with it. |
| Why do some pure substances have to be separated from some impurities in the industry? | •Left of reactants, or other products, may be harmful. |
| What can filtration be used for? | •Filtration can be used to separate a solid from a liquid or from a solution. |
| Energy changes in chemical reactions are carefully controlled. Explain why. | •Energy changes in the reaction affect the rate. •Containers for reactions may be damaged by extreme temperatures. |
| Crystallisation is used to purify solid crystals. State the several stages and what happens during it. | 1 •Dissolving - dissolve product in a small amount of water 2 •Filtration - filter solid impurities which did not dissolve. You are left with the FILTRATE 3 •Evaporation - the filtrate will start to crystallise as the water gradually evaporates. Cool the filtrate as this happens. 4 • Filtration (again) - filter off crystals, leaving soluble impurities in solution. 5 •Drying - dry crystals in a dessicator, or oven |
| What is the difference between theoretical yield and actual yield? | Theoretical yield •it is the predicted yield (how much you expect to see at the end) Actual yield •The mass of product measured at the end of the experiment (how much is actually there after) |
| What is the formula to find the percentage yield? | Percentage yield = actual yield/theoretical yield x 100 |
| What is the rate of reaction? | The rate of reaction is the amount of a product produced or the amount of reactant used up in a certain time. |
| Why do chemical engineers look for ways to control reactions? | •To make them more economical •To ensure that the reactions occur at a safe rate. |
| •What do chemical engineers have to consider when doing this? | •The cost of energy •Safety •How to make it economical |
| What needs to happen for reactions to occur? | •Particles must collide. |
| How do you increase the rate of the reaction in terms of particles and collisions? | •More collisions between particles = faster rate of reaction. |
| What is a catalyst? | A catalyst is a substance that speeds up a chemical reaction but is not used up. |
| When are reactions faster? | •The temperature of the reactants increase (particles vibrate more, so they are more likely to collide) •The size of solid particles are smaller (increases surface area - more chance to collide) •Concentration of reactants in solution increases (more particles - more collisions) |
| How do chemical engineers control the rate of reaction? | •Controlling factors that affect the rate such as temperature, concentration, particle size, or whether to use a catalyst. |
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