Acid and Bases

Question 1

what are the 5 definitions of acid and bases ?

Answer 1

Arrhenius 
Bronsted Lowry
solvent systems
lux-flood
Lewis

Question 2

how did Arrhenius define an acid?

Answer 2

an Arrhenius acid is one that when dissolved in an aqueous solution increases the concentration of H3o+ ions

Question 3

how did Arrhenius define a base?

Answer 3

an Arrhenius base is one that when dissolved in an aqueous solution increases the concentration of OH- ions

Question 4

what is a strong acid and a strong base according to Arrhenius?

Answer 4

A strong(100%) acid is one that completely dissociates in an aqueous solution to form H3O+ ions and anions while a strong (100%)bases is one that dissociates completely in an aqueous solution to form OH- ions and cations .

Question 5

3 examples of strong acids

Answer 5

HCl, H2SO4, HNO3, HBr, HI

Question 6

3 examples of strong bases

Answer 6

NaOH, KOH, CaOH, MgOH

Question 7

define weak acid and base according to Arrhenius

Answer 7

a weak bases(NH4OH) and acids(CH3COOH) are ones that do not completely ionize in an aqueous solution and exist in a reversible state.

Question 8

what are the limitations of Arrhenius’s definition?

Answer 8

Arrhenius definition is limited to aqueous solutions those containing H+ and OH- ions, acid and bases reaction can take place in other solvents.
there are basic compound that do not have an OH- group but still have basic properties and are not considered by this definition. eg NH3. This definition singles out OH has a source of base.

Question 9

How would you define an Arrhenius acid-base reaction?

Answer 9

An Arrhenius acid and base reaction is between an Arrhenius acid and Arrhenius base in a neutralization reaction to form a salt and water.

Question 10

what is a Bronsted Lowry acid?

Answer 10

A proton/ H+ donor

Question 11

what is a Bronsted Lowry base?

Answer 11

A proton/H+ acceptor

Question 12

define Bronsted Lowry acid-base reaction

Answer 12

The transfer of a proton/H+ from a Bronsted Lowry acid (proton donor) to a Bronsted Lowry base(proton acceptor) to form a conjugate acid and a conjugate base

Question 13

what is a conjugate acid-base pair?

Answer 13

A conjugate acid-base pair consist of 2 species in an acid-base reaction, one acid and one base that differ by the gain or the loss of a proton.

Question 14

what does the term amphiprotic mean?

Answer 14

An amphiprotic specie is one that can function as an acid or a base i.e they can gain or lose proton.

This is dependent on what they are reacting with. If an amphiprotic specie reacts with a stronger acid it will be the base and if it reacts with a stronger base it will be the acid.

Question 15

examples of amphiprotic species

Answer 15

H2CO3-, H2O

Question 16

How does water autoionize?

Answer 16

In pure water some molecules act as bases and some act as acids, these molecules can react and cause ionization of water hence this is know as autoionization( ionization of ones self.
2 H2O —-> H3O+ + OH-

Question 17

What is the equilibrium constant/ ion product constant of water?

Answer 17

Kw = 1.0 x 10-14 at 25 degrees Celsius

Question 18

true or false

acid strength increases going across the period

Answer 18

true

Question 19

why does acid strength increase going a across the period?

Answer 19

As you go across the period electronegativity(ability to attract electrons) increases, the more electronegative an atom the more stable it becomes. these molecules are not willing to give up electrons (they hold them tightly) to bind with H+ so there will be concentration of H+ ions thus increasing acidity. A less electronegative atom will form a bond with proton because it is less stable by itself.

Question 20

true or false

acid strength increases going up the group

Answer 20

false

Question 21

Why does acid strength increasing going down the group?

Answer 21

As you move down a period the atomic radius increases in size and hence the bond energy will decrease. bond strength overrides electronegativity when going down a group.
the ability for the atoms to accept electrons will decrease so there will be weak bonds forming between the proton and the conjugate base.

consider HF, F is highly electronegative so it will attract electrons towards itself and H-F will be hard bond to break. unlike HI, I is less electronegative so the bond will be easier to break to generate H+ ions hence making it more acidic

Question 22

what is an oxoacid?

Answer 22

an acid that contains hydrogen oxygen and at least one other element.

Question 23

describe the strength of oxoacids

Answer 23

Strength of an oxoacid depends on the number of O atoms present, specifically doubly bonded O and the electronegativity of the central atom(non-metal).
eg HCLO

The more electronegative central atom Cl will pull electron density from the O-H weakening the bonds and thus the H+ can ionize easily.

The oxygen atoms are electronegative, so they pull electrons towards them self. so if there is a lot of oxygen atoms there is a greater distribution of the negative charge. so the hydrogen atom is never attracted to anyone atom making the acid stronger
HCLO4> HCLO3> HCLO2>HCLO

Question 24

To examine the solvent system definition what do we need to consider first?

Answer 24

the auto dissociation /autoionization of the solvent

Question 25

explain auto dissociation of solvents

Answer 25

For protic solvents the proton is transferred from one solvent molecule to another forming a protonated cation of the solvent and a deprotonated anion of the solvent. For aprotic solvents it's the transfer of an atom to form a cation and anion.

Question 26

based on the solvent system definition define an acid and a base

Answer 26

an acid is a solute that produces the cation of the solvent while a base is the solute that produces the anion of the solvent.

Question 27

what is the difference between a protic solvent and an aprotic solvent?

Answer 27

A protic solvent has ionizable protons while a aprotic solvent does not.

Question 28

what are the categories of aprotic solvents?

Answer 28

polar, non ionized non polar, non ionized highly polar, autoionizing ( auto dissociate by transfer of F- ions)

Question 29

what is the lux-flood definition of acid and base

Answer 29

And acid O2- acceptor while a base is a O2- donor

Question 30

true or false | acidic nature increases as you move from left to right

Answer 30

true | metallic oxides tend to be basic and non-metal oxides are acidic

Question 31

what are amphoteric oxides? | give examples

Answer 31

an amphoteric oxide is one that can react with both acidic and basic oxides. examples include aluminum, zinc, copper beryllium

Question 32

define a lewis acid and a lewis base

Answer 32

a lewis acid is an electron pair acceptor while a lewis base is an electron pair donor

Question 33

what is formed when a lewis acid and base reacts

Answer 33

the compound formed is known as an adduct or a complex

Question 34

true or false | metal ions react with a ligand to form an adduct

Answer 34

true, but it is typically called a coordination compound. the metal cation is usually a lewis acid while the lignad is a lewis base

Question 35

an electron pair donor and and an electron pair acceptor can also be referred to as ?

Answer 35

They can be referred to as a nucleophile and an electrophile respectively

Question 36

what affects lewis acidity and basicity

Answer 36

lewis acidity and basicity is affected be the substituents electronic and steric effects

Question 37

explain how acidity and basicity can be lowered or increased

Answer 37

an electron withdrawing group will lower the basicity of a lewis base while an electron donating group will increase the basicity. an electron withdrawing group would increase the acidity of the lewis acid while the electron donating group would decrease the acidity

Question 38

explain the steric effect

Answer 38

for a Lewis acid and base reaction to be take place an electron pair must move from the highest occupied molecular orbital (HOMO) of the base to the lowest unoccupied molecular orbital(LUMO) of the acid. In order for the adduct to be stable both orbital need to have the right symmetry an overlap so that the bonding molecular orbital formed is lower in energy than the LUMO and HOMO orbitals