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Science C3 Topic 5
GCSE edexcel further additional chemistry: organic chemistry
Question | Answer |
---|---|
What is fermentation? | Fermentation is when microorganisms break down large molecules using enzymes |
What are the desirable conditions for fermentation? | * Anaerobic conditions - if oxygen is present then yeast will respire aerobically, producing only carbon dioxide and water * Warm temperature - if the temperature is too low the reaction is slow, and if the temperature is too high the yeast is killed |
What makes alcohol drinks different? | They contain different percentages of ethanol - drinks are rated in terms of the number of units of ethanol that they contain |
What are the impacts of drinking alcoholic drinks on the drinker? | Short-term: *Slower reaction times *Violent/aggressive behaviour *Loss of balance & coordination *Vomiting & fainting *Dehydration -> hangover Long-term: *Liver cirrhosis *Increases risk of heart disease and stroke |
What are the impacts of drinking alcoholic drinks on society? | *Lots of money is spent on helping those with alcohol-related medical conditions *Can cause anti-social behaviour and disorder in public places |
What are the three ways that ethanol can be produced? | * fermentation of glucose by yeast * fractional distillation of fermentation mixture * hydration of ethene |
How is ethanol produced by the fermentation of glucose? | Yeast is a single-celled fungus that breaks down glucose sugar into ethanol and carbon dioxide by aerobic respiration. The yeast cells release the enzymes for this reaction. The reaction is done at 30-40º as it is the optimum temperature for enzymes |
How is ethanol produced by fractional distillation? | 1. Fermentation mixture is heated 2. Vapour rises up fractionating column - fraction of the liquid that boils first will contain a higher proportion of ethanol (ethanol boiling point: 78ºC) 3.Vapour condenses + liquid is collected, up to 95% ethanol |
How is ethanol produced by the hydration of ethene? | Ethene is a hydrocarbon, produced by fractional distillation of crude oil + cracking larger molecules in higher-boiling fractions of crude oil. Ethene is reacted with steam in the presence of a catalyst - hydration reaction, water is added to ethene |
What is the reverse of this reaction? | This reaction can be reversed in a dehydration reaction - heating ethanol to a high temperature in the presence of a suitable catalyst produces ethene and steam |
What are some advantages/ disadvantages of producing ethanol by: fermentation of glucose? | Advantages: uses biofuels (sugar cane, sugar beet) which are renewable as they can be regrown Disadvantages: produces ethanol solution of only 15% concentration because higher concentrations deactivate the yeast, dependent on crop availability/ climate |
What are some advantages/ disadvantages of producing ethanol by: fractional distillation of fermentation mixture? | Advantages: uses biofuels (sugar cane, sugar beet) which are renewable as they can be regrown Disadvantages: dependent on the availability of crops and how easily they can be grown in different climates |
What are some advantages/ disadvantages of producing ethanol by: hydration of ethene? | Advantages: produces nearly 100% pure ethanol, little or no waste products Disadvantages: crude oil is a non-renewable, finite resource |
What is a homologous series? | A series of compounds which have features: *shared functional group *shared general formula *similar chemical properties *physical properties show a gradation eg. boiling points of alcohols alkanes + alkenes increase as no. of carbon atoms increases |
What are the boiling points of the first three alcohols? | methanol:-164 ethanol: -88 propanol: -42 |
Describe the features of the alkanes | * Functional group = only single bonds * Suffix = -ane * General formula = CnH2n+2 * Hydrocarbons * e.g. methane CH4 (one carbon atom with four hydrogen atoms around it, single bonds) |
Describe the features of the alkenes | * Functional group = double carbon-carbon bond * Suffix = -ene * General formula = CnH2n * Hydrocarbons * e.g. ethene C2H4 (a carbon-carbon double bond, 2 hydrogen atoms coming off either carbon atom) |
Describe the features of the alcohols | * Functional group = hydroxyl group (O-H) * Suffix = -ol * General formula = CnH2n+1OH * e.g. propanol C3H5OH |
Describe the features of the carboxylic acids | * Functional group = carboxyl group (COOH) * Suffix = -oic acid * General formula = C(n-1)H(2n-1)COOH = CnH2nO2 * e.g. propanoic acid C3H5OH |
What forms when ethanol is oxidised? When does this occur? | Ethanol can be oxidised to form ethanoic acid in aerobic reaction - this occurs when bottles of wine are left open |
Ethanoic acid is found in what foodstuff? | It is the main content of vinegar |
What is ethanoic acid used for? | • Ethanoic acid is a flavouring as it gives food a tangy, sharp taste • It is also a preservative - for example some foods are pickled (stored in vinegar) and the foods last longer because bacteria can’t survive in the acidic environment |
What shows that ethanoic acid acts as a normal acid? | * It turns litmus paper and universal indicator red * It forms ethanoate salts when they react with metals, metal hydroxides, bases and carbonates |
Metal + acid -> ? | Salt + hydrogen |
Metal hydroxide + acid -> ? | Salt + water (it is a neutralisation reaction, as hydroxides are bases) |
Metal oxide + acid -> ? | Salt + water (it is a neutralisation reaction as oxides are bases) |
Metal carbonate + acid -> ? | Salt + water + carbon dioxide |
sodium hydroxide + propanoic acid -> ? | Sodium propanoate + water |
Magnesium + ethanoic acid -> ? | Magnesium ethanoate + hydrogen |
What is an ester? | Esters are compounds made when carboxylic acids react with alcohol |
What is the reaction involving a carboxylic acid and an alcohol? | Carboxylic acid + alcohol -> ester + water |
methanoic acid + propanol -> ? | propyl methanoate + water |
What are the uses of esters? | * Used in perfumes, they are pleasant-smelling * Used as flavourings in sweets * Make polyesters (long chain of esters that can be made into fibres -> woven into fabrics) |
What can polyesters be recycled into? | Fleece clothing and fibres e.g in a carpet |