C10 Flashcards
What is a homologous series ?
It is a family of organic compounds with the same functional group
Whats the general formula for alkenes ?
CnH2n
Why are alkenes not used for fuels ?
Because there is complete combustion and they also release less energy per mole in combustion than alkanes
What makes alkenes more reactive than alkanes ?
Its the c-c double bond that makes alkenes more reactive than alkanes. Molecules that react with alkenes add to the alkene across their double bonds
What happens when alkenes react with bromine and whats the general formula for the reaction ?
The orange colour in bromine water comes from Br2 molecules, which are converted into a colourless product called dibromoethane when they react with a alkene
Ethene (alkene) + bromine —–> dibromoethane
What happens when a alkene react with hydrogen ?
Alkenes are unsaturated hydrocarbons therefore they dont contain the maximum amount of hydrogen atoms in the hydrocarbon molecule. But with the addition of H2 across the double bond of the alkene, will form a saturated alkane. This reaction takes place at 60 degrees celcius in the presence of a nickel catalyst.
What happens when a alkene reacts with water (steam) ?
Ethene is the main by-product in cracking and it can react with steam to make ethanol.
The reaction requires energy to heat the gases and to generate a high pressure
The reaction is also reversible so the ethanol can break back into ethene and steam
What is an alcohol ?
It is the same thing as an alkane but imagine taking one of the hydrogens and replacing it with OH
The functional group for alcohols is OH
What is a carboxylic acid ?
It has the functional group COOH and there is a double bond between one of the C and O atoms and then a single bond bewteen the other C and O atoms
What is an ester ?
If you replace the H atom in the COOH group by a hydrocarbon, such as CH3 or C2H5, you would get an ester.
An esters functional group is COO
What are alcohols used as?
Used as solvents and fuels
What is the main alcohol in alcoholic drinks ?
Ethanol
How is ethanol made by fermentation ?
Glucose —-> ethanol + carbon dioxide
How can ethanol be made in industry’s ?
By reacting ethene (obtained by cracking heavy fractions from crude oil ) and steam in the presence of a catalyst. But this method uses up crude oil
What is the general formula for alcohols reacting with oxygen ?
Alcohol + oxygen —-> carbon dioxide + water
What happens when alcohols react with sodium metal ?
Alcohols react with sodium metal to form a solution of sodium alkoxide and hydrogen gas is given off
How can ethanol be oxidised to ethanoic acid ?
Either by chemical oxidising agents or by the action of microbes in the air
Whats the general formula for oxidising alcohols ?
Ethanol + oxygen atoms from oxidising agents —–> ethanoic acid + water
Whats the main acid in vinegar ?
Ethanoic acid
What do carboxylic acids form when dissolved in water ?
They form acidic solutions
Carboxylic acids have the same typical reactions as all acids.
Whats the formula for ethanoic acid + sodium carbonate (acid + metal carbonate) ?
Ethanoic acid + sodium carbonate —–> sodium ethanoate + water + carbon dioxide
Why are carboxylic acids called weak acids ?
Carbon dioxide gas is given off more slowly when a metal carbonate reacts with a carboxylic acid, as compared with hydrochloric acid of the same concentration. That is because the carboxylic acids are weak acids, as opposed to strong acids, such as sulfuric acid or hydrochloric acid.
Remember that acids must dissolve in water before they show their acidic properties. That is because in water all acids ionise (split up).
Their molecules split up to form H+(aq) ions and negative ions (such as the ethanoate ions, CH3COO-(aq) from ethanoic acid). Strong acids ionise completely, whereas weak acids do not. In carboxylic acids, most of the molecules stay as they are (as CH3COOH molecules in ethanoic acid), and only a small proportion will ionise in their solutions. A reversible reaction takes place, in which the position of equilibrium lies well over to the left
Do carboxylic acid solutions have a higher pH (meaning a lower concentration of H+ ions) or lower than a strong acid ?
a carboxylic acid solution has a higher pH (meaning a lower concentration of H+ (aq) ions) than a strong acid, resulting in a slower reaction with a metal carbonate.
How can you make an ester ? And whats the general formula ?
Carboxylic acids react with alcohols to make esters
It is a reversible reaction and water is also formed
An acid usually sulfuric acid is used as a catalyst
Carboxylic acid + alcohol —-> acid catalyst —–> ester + water
