CARBOXYLIC ACIDS - ORGANIC 2

Question 1

What type of acids are carboxylic acids?

Answer 1

weak (only partially ionise in water)

Question 2

why do carboxylic acids have relatively high bp for their masses

Answer 2

as size increases the boiling point increases due to greater VDW forces and H bonding

Question 3

reaction for when H ions in water is transferred from carboxyl group to water molecule

Answer 3

CH2COOH +H20 <> CH3COO- +H30

OR

CH3COOH (aq) <> CH3COO- (aq) + H+(aq)

Question 4

properties of carboxylic acids

Answer 4

-can form H bonds with water > completely soluble in water up to 4 c
-form H bonds with another in solid state > higher mp than alkanes of similar Mr

Question 5

how to identify carboxylic acids

Answer 5

-measure mp and compare it with table of know mp
- thiele tube can be used/ mp can be found electrically

Question 6

What happens if the H from OH group of carboxylic acid is lost

Answer 6

-forms a carboxylate ion
-so negative charge is shared over the whole of carboxylate group
-this delocalisation makes the resulting ion more stable

Question 7

carboxylic acid reaction with metals

Answer 7

-MASH
-metal + acid > salt +hydrogen
- 2CH3COOH + Mg > (CH3COO)2Mg + H2
-dilute ethanoic acid + magnesium > colourless sol of magnesium ethanoate + hydrogen gas

Question 8

carboxylic acid reaction with bases

Answer 8

-neutralisation reaction - H ions from acid react with hydroxide ions
H+ (aq) + OH- (AQ_ > H20(l)

CH2COOH +NAOH > CH3COONa + H2O
ethanoic acid + sodium hydroxide > colourless sol of sodium ethanoate + water

Question 9

carboxylic acid with carbonates

Answer 9

-CASHCO
-2H(aq) + Co32- (s) > H2O(s) +Co2 (g)

• 2CH3COOH + Na2CO3 > 2CH3COONa + Co2 + H20
  ethanoic acid + sodium carbonate > sodium ethanoate + carbon dioxide + water

Question 10

carboxylic acid with hydrogen carbonate

Answer 10

CH3COOH + NaHCO3 > CH3COONA + H20+ Co2
ethanoic acid + sodium hydrogen carbonate > sodium ethanoate + water + carbon dioxide