959800
Descripción
Fichas por harry.vinall, actualizado hace más de 1 año
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Creado por harry.vinall
hace más de 10 años
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| Pregunta | Respuesta |
| What safety precautions should be taken when using chemicals? (get 3) | Make sure chemicals are stored carefully and labelled correctly; wear goggles gloves and protective clothing; be prepared for spills; don't put hazardous chemicals down the drains or in the normal rubbish; use the least dangerous chemicals possible. |
| What is chemical synthesis? | Combining simple substances to make a new compound. |
| What can we use to tell if a solution is alkali or acid? Explain the pH scale. | By using indicators. For example litmus turns red in acid and blue in alkali. Universal indicator can also test for alkali, indicating the pH of the substance. Substances which are neutral have a pH of 7 and turn green when indicator is added. The further under 7 you go the stronger the acid. A very strong acid turns red when indicator is added. The further above 7 you go the stronger the alkaline. A very strong alkali turns dark blue when indicator is added. |
| What is formed when a metal reacts with an acid? | A salt + hydrogen. |
| What is formed when acids react with metal oxides and hydroxides? What about with carbonates? | Oxides and hydroxides: a salt and water. Carbonate: a salt, water and carbon dioxide. |
| What is the second part of the name given to salts formed with the following acids: 1) hydrochloric 2) sulfuric 3) nitric | 1) Chloride 2) Sulfate 3) Nitrate |
| What is a salt? What ions are formed when the acids from the previous question react to form a salt? | Salts are ionic compounds made up of positive metal ions and negative acid ions. The formula for the salt combines the symbol of the metal and the acid. Chlorides contain cl- ions; sulfate (SO4)2- ions; nitrates contain (NO3)- ions. |
| What is titration? | If an acid is added to an alkali, or vica versa, one drop at a time they will slowly react until all of the acid/alkali is used up. One more drop of acid/alkali and the solution will change from alkali to acid, or visa versa. This is called the end-point. Titration involves measuring the volumes of acid and alkali needed to reach the end-point. |
| What is formed in all neutralisation reaction and why? | Water as the H+ hydrogen ions in the acid react with the OH- hydroxide ions in the alkali to form water (H2O) |
| What happens when an acidic compound dissolves in water? What about an alkaline compound? | Acid: Forms H+ ions and a negative ion. The hydrogen ions are what make the solution an acid. The pH indicates the amount of hydrogen ions in the solution. Alkali: Hydroxide OH- ions and a positive ion formed. |
| What are exothermic and endothermic reactions? | Exothermic: When heat is given out to the surroundings by a reaction. This means the products have less energy than the reactants as energy is lost to the surroundings. Endothermic: When energy is taken in from the surroundings causing the temperature to fall. This means the products have more energy than the reactants. |
| What are heat exchangers? | Tubes carrying water around or through the reaction vessels. Exothermic reactions heat up the water in the heat reaction vessels, in the same way as heat from natural gas is passed to water in a boiler. |
| In what two circumstances will filtration purify a product? | If the product is a solid and the impurities are in solution or if the product is soluble and the impurities are not. |
| How can crystallisation be used to purify a product? | Dissolve the product in water, then filter out insoluble impurities. The product is the filtrate. Evaporate some of the product until it starts to crystallise, the solution is then cooled while the product continues to crystallise. Then filter again, and the crystals will be collected in the filter. The remaining water can be evaporated from the crystals by placing them in an oven set at 60 degrees. Alternatively we could place the damp crysticals in a desiccator with a substance which absorbs water. |
| What is rate of reaction and how do we measure mean rate of reaction? | The amount of product produced or the amount of reactant used up in a certain time. Mean rate of reaction = change in quantity measured/ time taken for change. |
| Name at least 3 factors that affect rate of reaction. | Temperature; size of solid particles (smaller=quicker); concentration of reactants; presence of a catalyst. |
| How do catalysts work? | They speed up reactions because the reactant particles react more easily when they collide with the catalyst particles. The catalyst collides with many reactant particles so a small amount of catalyst can have a big impact on the rate of reaction. |
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