Theory

Question 1

ARRHENIUS
DEFINITION Acids

Answer 1

Substance that when dissovled in an aqueous solution produces H+ ions

Question 2

ARRHENIUS
DEFINITION Bases

Answer 2

Substance that when dissovled in an aqueous solution produces OH- ions

Question 3

Brownstead lowry Definition for Acids

Answer 3

Substance to donates H+/proton

Question 4

Brownstead lowry Definition for Bases

Answer 4

Substance to accepts H+/proton

Question 5

Explain why the acid strength decreases as protons (H+) are removed successively from a polyprotic acid such as H3PO4.

Answer 5

With loss of each proton (H+), the molecule increases in negative charge. Since protons are positive, protons are
more strongly attracted, thus more difficult to donate proton

Question 6

Amphiprotic meaning?

Answer 6

Ability to donate and accept protons.

Question 7

What is ACIDITY CONSTANT

Answer 7

measures the extent of proton transfer and acidity strenght.

Question 8

What does high value of Ka represent

Answer 8

= high concentration of products

Question 9

Monoprotic?

Answer 9

Donates one H+

Question 10

Polyprotic

Answer 10

• donates more than one H+ per molecule

Question 11

diprotic How many H+ protons in steps and give example with H2SO4

Answer 11

Donates 2 H+,
i. H2SO4(l) + H2O(l) → HSO4 - (aq) + H3O + (aq) complete ionisation
ii. HSO4 - (aq) + H2O(l) ⇌ SO4^2- (aq) + H3O + (aq) partial ionisation
❖ Solution of H2SO4 contains HSO4 - ,H3O + and SO4^2-

Question 12

triprotic 3 H+ protons; degree of ionisation decreases at each step

Answer 12

i. H3PO4(l) + H2O(l) ⇌ H2PO4- (aq) + H3O^+ (aq)
ii. H2PO4^2- (aq) + H2O(l) ⇌ HPO4^2-(aq) + H3O+ (aq)
iii. HPO4^2- (aq) + H2O(l) ⇌ H3O+ + PO4^-3 (aq)

Question 13

What does double arrow mean

Answer 13

denotes weak acid that does not completely ionise

Question 14

What does the Ka Value represent explaination

Answer 14

Since Ka is the ratio of concentration of products to concentration of reactants, the higher the value means the higher the concentration of products. Hence, the equilibrium position shifts to the right, favoring the products, hence meaning greater tendency for acid to form hydrogen ions, and hence, the stronger the acid.

Question 15

What is conjugate base

Answer 15

formed after a weak acid donates a proton

Main - Donates a proton

Question 16

What is a conjugate acid

Answer 16

where it accepts a proton

Question 17

what produces a strong conjugate base

Answer 17

a weak acid

Question 18

what produces a weak conjugate acid

Answer 18

a strong basew

Question 18

what produces a strong conjuugate acid

Answer 18

a weak base

Question 19

what produces a weak conjugate base

Answer 19

a strong acid

Question 20

what is self ionisation

Answer 20

Where water molecules react with eachother to form an equilibrium reaction

h2o+ h2o —> h3o+ + oh-

Question 21

what is the temperate and value of equilibrium constant for all aq soln.s

Answer 21

At 25°C or 298 K:
−
Kw = [H3O+][OH-] = 1.00 x 10-14

Question 22

Is self ionisation exothermic or endothermic

Answer 22

endothermic

Question 23

How do we know when a solution is basic

Answer 23

[H3O+] < [OH-]

Question 24

how do we know when a solution is acidic

Answer 24

[H3O+] > [OH-]

Question 25

How do we know when a solution is neutral

Answer 25

[H3O+] = [OH-]

Question 26

formula to find conc from ph ?

Answer 26

[H3O+] = 10^-pH or [H+] = 10^-pH

Question 27

What is a neutralisation equation?

Answer 27

Strong acid +Strong base * No hydrolysis Strong acid/base produce very weak conjugate base/acid Thus, no hydrolysis

Question 28

is Strong acid + weak base, neautral acidic basic?

Answer 28

acidic

Question 29

Strong base + weak acid neautral acidic basic?

Answer 29

basic

Question 30

Weak acid + weak base neautral acidic basic?

Answer 30

Depends on Ka and Kb value - Ka > Kb acidic * Ka < Kb basic * Ka = Kb neutral

Question 31

what is the Process to determine acidity of salt

Answer 31

look at parent acid and base

Question 32

Using Le Chatelier’s principle, predict what will happen if a solution containing hydrogen ions is added to a solution of hydrochloric acid

Answer 32

HCL + H2O ---> Cl- + H3O+ Added hydrogen ions will increase the concentration of hydrogen ions. Since HCl completely ionises, the reaction goes to completion, not reversible. (Since the OHconcentration is extremely small due to self-ionisation of water, it has negligible reaction with added H+) Concentration of hydrogen ions stay high.

Question 33

A solution containing hydrogen ions is added to a solution of hydrofluoric acid?

Answer 33

HF will partially ionise hence, Added hydrogen ions will increase the concentration of hydrogen ions. LCP predicts to partially counteract this by decreasing the concentration. Equilibrium is shifted to the left, reverse reaction is favoured, decreasing the concentration of hydrogen ions until equilibrium is reestablished. The final concentration will be however higher than the initial concentration (partially counteract)

Question 34

Write an equation showing the addition of acetic acid to water.

Answer 34

ch3cooh + h2o ---> ch3coo- + h3o+

Question 35

Explain what the term ‘buffering capacity’ means at the molecular level.

Answer 35

Ability of buffer solution to neutralise added acid or base without a significant change in pH

Question 36

How to identify if a salt is acidic or basic or neutral

Answer 36

look at parent acid and base hence - split the salt into cation and anion and then the cation become a base by adding OH- and the anion becomes a acid by adding a H+ Hence if strong acid and weak base = acidic since greater H3O+ than OH- conc. etc vice versa

Question 37

Even though sulfuric acid contains two hydrogen atoms capable of ionisation, a solution does not contain two times as many hydrogen ions as a solution of HCl with the same concentration. Explain why not.

Answer 37

A polyprotic acid will hold on to its H atoms more stongly once one has been removed because it already has a negative charge at that point.

Question 38

What is conc of H3O+ and OH- at 25 degrees celcius

Answer 38

1x10^-14

Question 39

Do water conduct electricity due to presence of ions from self ionisation? explain

Answer 39

Pure water is very poor conductor as it does contain some ion from self ionisation of h2o but their concentration are very low hence cannot properly conduct.

Question 40

For Self ionisation endothermic reaction write equation and of h2o and its dissociation and explain when T increased using shift and effects on conc

Answer 40

T increase, shift right hence conc of products increase hence Kw increases therefore h+ conc increases and ph decreases as inversely proportional. ph decreases but neutral as conc of h+ = oh-

Question 41

An unknown solution is measured to have a pH of 7 at 10 degrees Celsius. Explain whether your solution is acidic, alkaline, or neutral. And note that the pH of water at this temperature is 7.27 when Kw equals 2.93 times 10 to the power of negative 15 at 10 degrees Celsius.

Answer 41

A pH of 7 at 10 degrees Celsius is slightly acidic as at 10 degrees concentration of OH- and H+ will be equal at pH of 7.27. Hence, since the value of 7 is lower than this, hence excess of hydrogen plus ions at 10 degrees Celsius. Hence pH is only neutral at 25 degrees Celsius.

Question 42

use bronsted lowry theory to explain why ph of ammonia solution is greater than 7 at 25 celicus, include one equation.

Answer 42

equation of bronsted lwory with water labels acid base conjugate acid and conjugate base oh- conc greater than h+ conc

Question 43

Write hyrdolysis equation between oxalic acid and h2o

Answer 43

two equations hc2o4- and h3o+ c2o42- and h3o+

Question 44

Write hyrdolysis equation between sulfuric acid and h2o

Answer 44

two equations

Question 45

what is ph range of sulfuric acid and h2o if 0.1M and 0.2M

Answer 45

1 and 0.7

Question 46

write ionic equation of ethanoic acid and zinc metal

Answer 46

Zn+2CH3​COOH→Zn(CH3​COO)2​+H2​ Zn+2CH3​COOH→Zn2++2CH3​COO−+H2​

Question 47

write ionic equation of ethanoic acid and barium carbonate solid

Answer 47

BaCO3​+2CH3​COOH→Ba(CH3​COO)2​+CO2​+H2​O BaCO3(s) + 2CH3COOH(aq) → Ba²⁺(aq) + 2CH3COO⁻(aq) + CO2(g) + H2O(l)

Question 48

Explain why the pH of sulfuric acid will be between 1.7 and 2. Justify with suitable equations , given conc of sulfuric is 0.02 originally

Answer 48

two equations. First equation ionises completely and second equation ionises partially. Therefore, concentration of H+ ions will be more than 0.01 but less than 0.02. show ph calculations

Question 49

The Bronsted-Lowry theory of acids and bases introduced the concept of the hydronium ion, H3O+(aq), as well as conjugate acid-base pairs. Explain what the ‘H3O+(aq)’ notation is referring to and why it is often used in preference to the ‘H+(aq)’ notation.

Answer 49

refers to the donation of a proton to a water molecule - more accurate representation of what occurs in aqueous solution / displays the conjugate nature and reversibility of acid/base reactions 2018 WATP Q 33 sem 1

Question 50

State whether the solution of Na2HPO4(aq) is acidic, basic or neutral, and explain what information this provides regarding the equations in part (b).

Answer 50

Basic The hydrolysis equation producing OH-(aq) occurs to a greater extent than the hydrolysis producing H3O+(aq). Therefore the [OH-] > [H3O+]