The Brønsted-Lowry Theory

Question 1

an acid is

Answer 1

a proton (H+) donor

Question 2

a base is

Answer 2

a proton (H+) acceptor

Question 3

a conjugate acid-base pair consists of

Answer 3

either a base and its conjugate acid or an acid and its conjugate base

Question 4

a conjugate acid of a base is

Answer 4

the species formed when a base accepts a proton

Question 5

a conjugate base of an acid is

Answer 5

the species formed when an acid donates a proton

Question 6

an amphoteric substance is

Answer 6

a substance than can act both as an acid and as a base

examples are: water

Question 7

in the Brønsted-Lowry theory, acids and bases are defined by

Answer 7

the way they react with each other

Question 8

a substance only behaves as an acid if the hydrogen carries

Answer 8

a slight positive charge

Question 9

hydrogen has a slight positive charge when it is bonded to

Answer 9

a highly electronegative atom in the right side of the Periodic table, such as oxygen or a halogen

Question 10

in order to accept a proton, a base must have

Answer 10

a lone pair of electrons

Question 11

the lone pair of electrons in the base is used to form a

Answer 11

dative covalent bond with the proton (H+)

Question 12

therefore, bases must contain an element from the …………side of the Periodic table which has a lone pair, usually……………

Answer 12

right hand side

oxygen

Question 13

when hydrogen chloride dissolves in water, the following equilibrium reaction takes place:

Answer 13

HCl(aq) + H2O(l) ⇌ H3O (aq) + Cl-(aq)

Question 14

HCl(aq) + H2O(l) ⇌ H3O (aq) + Cl-(aq)

• In the forward reaction, the HCl acts as ………………because: ………………….and the H2O acts as…………….because……..
• In the reverse reaction, the H3O+ acts as…………because…………….and the Cl- acts as…………………because

Answer 14

HCl(aq) + H2O(l) ⇌ H3O (aq) + Cl-(aq)

• HCl acts as an acid because it donates a proton to the H2O
• H2O acts as a base because is accepts a proton from the HCl
• H3O+ acts as an acid because it donates a proton to the Cl-
• Cl- acts as a base because it accepts a proton from the H3O+

Question 15

identify the conjugate acid-base pairs in the following reaction:
HCl(aq) + H2O(l) ⇌ H3O (aq) + Cl-(aq)

Answer 15

• HCl and H2O

- H3O+ and Cl-

Question 16

Identify the conjugate pairs in the following reaction:

HCl(aq) + H2O(l) ⇌ H3O (aq) + Cl-(aq)

Answer 16

• Cl- is the conjugate base of HCl

- H2O is the conjugate base of H3O+

Question 17

a diprotic or dibasic substance is

Answer 17

an ACID that can donate two protons, such as H2SO4

Question 18

sulfuric acid is dibasic. write down the two steps for the reaction of sulfuric acid to donate two H+ ions

Answer 18

H2SO4 = H+ + HSO4-
HSO4- = H+ + SO4 2-

Question 19

a diprotic or diacid substance is

Answer 19

a BASE that can accept two protons, such as CO3 2-

Question 20

the reaction of the carbonate ion to receive two protons is:

Answer 20

CO3 2- + H+ = HCO3-

HCO3- + H+ = H2CO3

Question 21

• when ammonia dissolves in water, an equilibrium is established, shown in the equation:
• identify the conjugate acid-base pairs

Answer 21

NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

NH3 and NH4+
H2O and OH-

Question 22

in the reaction with HCl, H2O acts as……………..because it…………..a proton while in the reaction with NH3, H2O acts as ………………because it……………….a proton. Therefore water is described as being ………………………

Answer 22

• H2O is a base with HCl as it accepts a proton
• H2O is an acid with NH3 as it donates a proton
• Amphoteric or amphiprotic

Question 23

all……………are……………………but not all……………………….are……………………

Answer 23

all amphiprotic substances are amphoteric but not all amphoteric substances are amphiprotic

Question 24

amphiprotic substances are those that

Answer 24

can both donate and accept protons

examples are: water, amino acids and HSO4- (hydrogensulfate ion)

Question 25

an acid can also be described as being an

Answer 25

electron pair acceptor

Question 26

a base can also be described as being an

Answer 26

electron pair donor