Acid and base reactions term 2 wace

Question 1

Define amphiprotic substance and examples

Answer 1

Substance that can donate or accept protons depending on what they are reacting with. Therefore can behave as acids/bases.
e.g. H2O, HCO3, H2PO4, HPO4,HSO4

Question 2

Define monoprotic acids and examples

Answer 2

Can donate only one proton (acidic proton) per molecule
e.g. HCL, HF, HNO3, CH3COOH (can only donate proton part of highly polar O-H bond)

Question 3

Define polyprotic acids.

Answer 3

Donate more than one proton from each molecule depending on the acids structure.

Question 4

Examples of di and triprotic acids

Answer 4

Di: donate two protons
e.g. H2S04 and H2CO3
Tri: donate 3
e.g. H3PO4

Question 5

How is the strength of an acid determined

Answer 5

Its ability to donate hydrogen ions to a base
strong acids donate a proton more readily than weak acids

Question 6

how is the strength of a base measured

Answer 6

its ability to accept hydrogen ions from an acid
strong bases accept hydrogen more readily than weak bases

Question 7

Strong acids examples

Answer 7

HNO3, HCL, H2S04, HBR, HI,

Question 8

Weak acids examples

Answer 8

CH3COOH, H2CO3, H3PO4, NH4

Question 9

Strong base examples

Answer 9

NaOH, KOH, Ca(OH)2

Question 10

Weak base examples

Answer 10

NH3, CH3COO-, CO3

Question 11

Explain the relative strength of conjugate acid-base pairs

Answer 11

The stronger an acid is, the weaker the conjugate base. The stronger the base, weaker the conjugate acid.

Question 12

Define what occurs in a reaction with a weak acid

Answer 12

double arrows
the reaction is reversible as the acid has only partially ionised

Question 13

Excluding their ability to donate/accept H+ ions, how else is the strength of acids/bases described?

Answer 13

In terms of the position of eqm when the substance donates/accepts a hydrogen ion to/from water
called hydrolysis reaction

Question 14

Define Ka (write the formula)

Answer 14

-acidity constant
eqm constant for hydrolysis reaction of an acid

Question 15

Why does waters conc not appear in constant formula?
What is it’s use in hydrolysis

Answer 15

It’s concentration is virtually constant=1
It is a weak electrolyte

Question 16

Define Kb (write the formula)

Answer 16

-basicity constant
eqm constant for hydrolysis reaction of a base

Question 17

Define dilution

Answer 17

adding more solvent to a solution

Question 18

What is the ionisation constant of water

Answer 18

Kw=1.00x1^-14]=[OH][H3O]

Question 19

Define salts and their formation

Answer 19

Formed in neutralisation reactions resulting in a compound whose positive ions come from a base and negative ions from an acid

Question 20

Describe the pH of salts of strong acid/strong base reaction e.g.

Answer 20

neutral salt
e.g. NaNO3
-Na can not hydrolyse=neutral
-NO3 from strong acid therefore a weak base so cannot react

Question 21

Describe the pH of salts of strong acid/weak base reaction e.g.

Answer 21

salts are acidic
weak base forms a conjugate acid which can hydrolyse
e.g. NH4Cl
-NH4 is acid from weak base can hydrolyse
-Cl cannot hydrolyse (neutral)

Question 22

Describe the pH of salts of weak acid/strong base reaction e.g.

Answer 22

basic salt
anions from weak acid hydrolyse with water=hydroxide ions
e.g. CH3COONa
-CH3COO can hydrolyse as conjugate base from weak acid
-Na cannot hydrolyse

Question 23

Describe the pH of salts of weak acid/weak base reaction e.g.

Answer 23

hard to predict
resulting pH depends on extent to which each reaction occurs

Question 24

Define neutral ions=neutral pH

Answer 24

-group 1 and 2 ions (Na K Ca Mg)
-Conjugate neg ions of strong acids

Question 25

Define ions form acidic solutions

Answer 25

-conjugate pos. ions of weak bases (NH4)
-Group 13 and transition metals (Al and Fe)
-HSO-4 H2PO4-

Question 26

Define ions form basic solutions

Answer 26

-conjugate neg ions of weak acids (CH3COO F CN)
-HCO3 CO3
-HPO4 PO4
-SO4

Question 27

Define and compare the acid/base models that have been used: Arrhenius and Bronsted-Lowry.

Answer 27

Bronsted-Lowry: acids are proton donators while bases are proton acceptors.

Arrhenius: acids dissociate and ionise in water to produce H+ ions
bases dissociate in water to produce OH- ions

Question 28

Provide an examples of dissociation reaction vs hydrolysis of HCl

Answer 28

dissociation:
HCl(g)+H2O(l)–>H3O+(aq)+Cl-(aq)
hydrolysis:
HCl(q)–>H+(aq)+Cl-(aq)