carboxylic acids

Question 1

what are the IUPAC rules for naming carboxylic acids

Answer 1

1. select longest chain of carbon atoms starting with the COOH group
2. remove e and add - oic acid after basic name
3. number chain nearest COOH
4. prefix with akyl substituents

Question 2

name this carboxylic acid

HCOOH

Answer 2

methanoic acid

(formic acid)

Question 3

name this carboxylic acid

CH3COOH

Answer 3

ethanoic acid

(acetic acid)

Question 4

name this carboxylic acid

C6H5COOH

Answer 4

benzene carboxylic acid

(benzoic acid)

Question 5

why do the boiling points of the carboxylic acids increase as chain length increases

Answer 5

due to increased Van Der Waals forces and hydrogen bonding

Question 6

out of these organic substances which has the highest boiling point:

butane
propan-1ol
ethanoic acid
propanal

Answer 6

ethanoic acid
(due to the ability to form 2x as many hydrogen bonds than propan-1-ol)

Question 7

give the solubility of carboxylic acids and explain this property

Answer 7

carboxylic acids are soluble in organic solvents and water as they hydrogen bond

Question 8

as the mass of carboxylic acid increases why does the solubility of the carboxylic acid decrease?

Answer 8

relying on Van Der Waals to dissolve the longer chain in water

and Van Der Waals are constantly breaking and reforming, making these less strong than H bonds

But there is 1 H bond and a lot more v.d.w

Question 9

give the 2 properties of benzene carboxylic acid in terms of solubility and explain these properties

Answer 9

benzene carboxylic acid is fairly insoluble in cold water but soluble in hot water

this is because benzoic acid is a non polar molecule as the temperature increases the electrons start to move allowing the hydrogen bonds to form and allows the molecule to do ionisation

Question 10

explain how carboxylic acids work as acids and give the symbol equation

Answer 10

H+ ions are transferred from COOH group to water

CH3COOH + H20 ⇌ CH3COO- + H3O+

CH3COOH (aq) ⇌ CH3COO- (aq) + H+ (aq)

Question 11

what type of acid are carboxylic acids and how do we know this

Answer 11

weak acids as they don’t completely dissociate

( the double headed arrow shows a partial dissociation)

Question 12

what is the general word equation for when a:

carboxylic acid + metal

Answer 12

carboxylic acid + metal —> salt + hydrogen

(MASH)

Question 13

what is word equation when :

ethanoic acid + magnesium

Answer 13

ethanoic acid + magnesium —> magnesium ethanoate + hydrogen

Question 14

write the symbol equation for the reaction of ethanoic acid and magnesium

Answer 14

2CH3COOH + Mg –> (CH3COO)2 Mg +H2 (g)

Question 15

what can be observed when magnesium reacts with ethanoic acid

Answer 15

produces a colourless solution of magnesium ethanoate and Hydrogen

Question 16

what happens in a neutralisation reaction

Answer 16

hydrogen ions from an an acid react with hydroxide ions

Question 17

are neutralisation reactions endothermic or exothermic

Answer 17

exothermic

Question 18

finish the word equation for the reaction between:

ethanoic acid + sodium hydroxide

Answer 18

BASH20

ethanoic acid + sodium hydroxide —> sodium ethanoate + H2O

Question 19

write the symbol equation for the reaction between ethanoic acid and sodium hydroxide

Answer 19

CH3COOH + NaOH –> CH3COONa + H2O

Question 20

write the general ionic equation for a neutralisation reaction

Answer 20

H+ (aq) + OH- (aq) —-> H2O (l)

Question 21

write a word equation for the reaction of sodium carbonate and ethanoic acid

Answer 21

(CASH20CO2)

sodium carbonate + ethanoic acid —> sodium ethanoate + water + carbon dioxide

Question 22

write a symbol equation for the reaction of sodium carbonate and ethanoic acid

Answer 22

Na2CO3 + 2CH3COOH —-> 2CH3COONa + CO2 + H20

Question 23

write the general ionic equation for the reaction of a carbonate and a carboxylic acid

Answer 23

H+ (aq) + HCO3- (s) —> H2O (l) + CO2 (g)