Acids and Bases

Question 1

What is a Bronsted acid?

Answer 1

Any substance that can donate a proton to another substance

Question 2

What is a Bronsted base?

Answer 2

Any substance that can accept a proton

Question 3

What is an amphiprotic species?

Answer 3

A species that can act as either an acid or a base

Question 4

What is a triprotic acid?

Answer 4

A substance that can donate up to three protons on reacting with H2O

Question 5

If the K value of an acid is high then the acid is…?

Answer 5

Strong

Question 6

Would Cl, NO2, CO2 strengthen or weaken an acid?

Answer 6

Strengthen

Question 7

Arrange in order of acid strength: Alcohols, Carboxylic acids, Phenols

Answer 7

Alcohols, phenols, carboxylic acids

Question 8

Would the presence of a Ch3 substituent increase the acidity of a phenol?

Answer 8

No-Ch3 is electron donating

Question 9

The harder it is to remove a proton from a species, the …. the acid

Answer 9

Weaker

Question 10

The higher the electronegativity of the atom that H is bonded to, the … the acid

Answer 10

Stronger

Question 11

What is an oxoacid?

Answer 11

An acid which contains an oxygen

Question 12

Why does having more electronegative atoms attached to the central atom increase acid strength?

Answer 12

The negative charge on the resulting anion is more easily delocalised with more electronegative atoms, making it more stable

Question 13

Kw is called

Answer 13

The autoprotolysis constant of water

Question 14

In a weak acid calculation, the concentration of the conjugate base is equal to that of the…?

Answer 14

Concentration of H3O+

Question 15

In a weak acid calculation, the concentration of the acid is equal to …?

Answer 15

The initial concentration - H3O+ concentration

Question 16

In a salt calculation, the concentration of the conjugate base is equal to…?

Answer 16

The initial concentration - OH- concentration

Question 17

In a salt calculation, the concentration of the acid is equal to…?

Answer 17

Concentration of OH-

Question 18

What is the equivalence point of a titration?

Answer 18

The point at which exactly equal stoichiometric amounts of acid and base have been reacted eg. where precisely the right amount of OH- has been added to convert all of the acid into its conjugate base

Question 19

What is the end point of an indicator?

Answer 19

The point at which it changes colour

Question 20

What is an indicator?

Answer 20

A weak acid for which the acid and conjugate base have different colours

Question 21

What is the formula for calculating the pH at an equivalence point of a titration?

Answer 21

pH= 7 + 1/2xpKa + 1/2xlog(concentration of conj base at equivalence point)

Question 22

Why is pK1 always less than pK2?

Answer 22

The loss of the first proton is easier than the second so the first step is always more favoured

Question 23

Where on a titration curve is equal to pK2?

Answer 23

The second buffer zone

Question 24

Which species are present in the first buffer zone?

Answer 24

Equal concentrations of the original species and its conjugate

Question 25

Which species is predominantly present at the first equivalence point?

Answer 25

The conjugate of the original species in the flask

Question 26

What is the major buffering pair used in blood?

Answer 26

H2CO3 and HCO3-

Question 27

What is the concentration of H2CO3 in blood controlled by?

Answer 27

Respiration

Question 28

What must the pH of the ocean be?

Answer 28

8.4

Question 29

Which dye colours poppies and cornflowers?

Answer 29

Cyanidin

Question 30

Which two functional groups do proteins contain?

Answer 30

Carboxylic acid and amine

Question 31

What is a zwitterion?

Answer 31

A dipolar ion that contains ionic groups of opposite charge and is overall neutral formed by internal proton transfer

Question 32

What is the isoelectric point? (pI)

Answer 32

The pH at which the majority of species is the zwitterions

Question 33

What is a technique used to separate amino acids?

Answer 33

Electrophoresis

Question 34

If a species has a low pI, which electrode will it be attracted to during electrophoresis?

Answer 34

The positive one, as low pI corresponds to high pH

Question 35

What is electrophoresis?

Answer 35

The separation of amino acids based on their isolectric points

Question 36

What is acid rain?

Answer 36

Rain with a pH greater than 7 due to dissolved gases such as SO3, SO2 and NO2

Question 37

Why do weak acids have high pHs?

Answer 37

It does not dissociate completely, so the equilibrium lies to the left so the concentration of H3O+ is less than the concentration of the acid