14775884
Descrição
FlashCards por Farha Idrees, atualizado more than 1 year ago
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Criado por Farha Idrees
quase 6 anos atrás
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| Questão | Responda |
| What happens when hydrocarbons burn in plenty of air? | • they transfer a lot of energy to the surroundings • the carbon and hydrogen in the fuel are completely oxidised and form carbon dioxide and water |
| Give the word equation for the oxidation of propane. | propane + oxygen ---> carbon dioxide + water |
| How do test the gases formed in complete combustion of a hydrocarbon? | 1. carbon dioxide turns limewater cloudy 2. the water turns blue cobalt chloride paper pink |
| What happens when there is not enough oxygen? | incomplete combustion occurs: • a toxic gas, CO, carbon monoxide is produced |
| Why is carbon monoxide dangerous? | • it is colourless and odourless • your red blood cells pick up this gas and carry it around in your blood instead of oxygen |
| What other gases are formed? | poisonous gases such as nitrogen oxide and sulphur dioxide can also form |
| What is the problem with larger hydrocarbons? | • they are thick liquids with high boiling points • difficult to vaporise • do not burn easily • are poor fuels |
| define cracking | breaking larger, less useful hydrocarbon molecules into smaller, more useful ones |
| Describe the process of cracking. | 1. a heavy fraction from crude oil is heated/vaporised 2. a) it is passed over a hot catalyst, or b) mixed with steam and heated to a very high temp 3. thermal decomposition reactions take place 4. the large molecules split apart to form smaller, more useful ones |
| What are the products of cracking? | cracking produces saturated hydrocarbons, used as fuels, and unsaturated hydrocarbons |
| Give an example of cracking. | • decane is a medium-sized alkane molecule • when it is heated to 500C with a catalyst it breaks down • this cracking reaction is an example of thermal decomposition decane = pentane + propene + ethene |
| What is a positive test for an unsaturated hydrocarbon (alkene)? | it turns orange bromine water, colourless |
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