Exam Pratice Three

Question 1

What is the poH of a sodium with (OH-) ?

Answer 1

120um = 120 x10-6

pOH=-log (120x10-6) =3.9
pH=14-3.9=10.1

Question 2

What is the pH of the solution of 0.125M?

Answer 2

poH=-log(0H)

poH -log (0.125)=0.90

pH=14-0.9=13.1

Question 3

Calculate the PH and the H+ concentration of following solution .

Answer 3

pOH = - log (0.02) = 1.7
pH = 14 -1.7 = 12.3 (using pH + pOH = 14)

(b) 12.3 = - log [H+]
antilog (-12.3) = 10-12.3 = [H+] in M
[H+] = 5 × 10-13 M = 500 × 10-15 M = 500 fM

Question 4

What is the Solution of (H+) 5 mM ?

Answer 4

H+=5mM
ph=-log(5x10-3)=2.3
pOH=14-2.3=11.7-H+

Question 5

What is the pOH of a solution with (OH-) ?

20mM?

Answer 5

1. H+=20mM

pH= -log (20x10-3)=1.69-1.7
PoH=14-1.7=12.3

Question 6

What is the pH of a solution with H + 20nm ?

Answer 6

20x10-9 M= 20x10-8
pH=-log (H+)
-log (2x10-8)
7.7

Question 7

What is the pH of a solution with H+ 10nm ?

Answer 7

10x10-9=10x10-8

-log(H+)
-log(1x10”8)
=8

Question 8

A number which is greater than 10 moves which direction ?

Answer 8

Left

Question 9

A number less than 10 moves which direction ?

Answer 9

Right

Question 10

What does 4230?

Answer 10

4.23x10”3

Question 11

What does 150000 ?

Answer 11

1.5x10”5

Question 12

What is acid ?

Answer 12

Acid is defined as a substance which gives up a hydrogen proton

Question 13

What is a base ?

Answer 13

Accepts a proton .

Question 14

Is a H+ ion a proton ?

Answer 14

Yes because if hydrogen ion looses its electron all that’s left is proton which comprises nucleus

Question 15

How do hydrogen atoms turn into an ion ?

Answer 15

Due to bonding with two water molecules h20 . The hydrogen atoms leave the electron behind and becomes H+ . (Hydrogen ion) as a single proton which a change o 1 +.

However, the water molecules has lost a proton becoming OH- having a charge of 1 - .It then binds to other molecules becoming hydronium ion (h30) producing a chemical reaction .

2h20 reversible reactions h30 OH-

Question 16

What happens during the reaction ?2h20 reversible reactions h30 OH-

Answer 16

Water molecule donates h20 one molecule donating a H+ serves an acid . It reverse reaction the OH- accepts the proton and becomes a base .Base means a compound carrying OH-

Question 17

Does H + exists on its own ?

Answer 17

No because is used to represent t H30 + but does not exists on its own always associates with water molecules in order to form H30 +

Question 18

Reaction reversed ? What happens the other way ?

Answer 18

2h20 reversible reactions h30 OH-

It reaches a state of equibirum, when they dissociate at the same rate they are being reformed from H+ and OH-.During the equibirum state known as self association of water proceeds in both directions .

Question 19

What happens to pure water

Answer 19

The pure water is extremely rapid happens in very y small proportion of water molecules .The concenration of water greatly exceeds the concentration of H+ and of OH- are equal in water

Question 20

What disrupts the balance?

Answer 20

By acids and bases

Question 21

What does acid donate when its dissolved in water ?

Answer 21

It donates H + to the soliution ,However, an acid increases the hydrogen ions

HC1-H+ + C1- Acidic Solution

Question 22

What is a substances which reduced hydrogen ions ?

Answer 22

Base how do they do this by reducing H + concentration by accepting hydrogen ions .

Question 23

What does a single arrow show ?

Answer 23

It can break up easily .These compounds dissociate completely when mixed with water , so hydrocholic aicd called syrong acid and sodium hydroxide called srong base . Na+ + OH+

Question 24

What are weak acids ?

Answer 24

They are acids which release reversibly .

Question 25

What is acid base which is conjugate ?

Answer 25

are compounds that differ by the presence of one proton, or H+. All acids have a conjugate base, which is formed when their proton has been donated; likewise, all bases have a conjugate acid, formed after they have accepted a proton.

Question 26

What is Buffer ?

Answer 26

Its a substance which tries minimise changes in concentration of H+ and OH- in a solution .It does by accepting hydrogen ions from the solution when its decreased .

Question 27

What do Buffers help with ?

Answer 27

Buffers helps allows biological fluids to maintain a constants pH despite the addition of acids/bases.
Consists of weak acids or its conjugate base /weak base and conjugate acid .

Question 28

Carbonic acid How is it formed ?

Answer 28

Its formed when Co2 reacts with water in blood plasma. Carbonic acids dissociates to yield a bicarbonate ion .Both these process causes pH to drop following the addition of acid than if acid has been added to pure water .

Question 29

What happens during this reaction ? H2C02 reversible H30 + Hco3

Answer 29

The excess H+ is neutralised and the pH will drop due t the acid being added .

OH- neutralised and the pH will increase due to less adding of alkali than if acid had been added .pH is minimised changed in pH solution .

Question 30

What are the three catartogies ?

Answer 30

Neutral : There’s equal amounts of OH-/H - substances

Acids : Greater amounts of H + substances

Base : greater amounts of OH-

Question 31

What does PKA determine ?

Answer 31

Determined the acids strength

The lower the pKa the stronger the acid .

Stronger acids deprotonate completely this is because of transfer of every acidic proton to solvent etc. .

Weak acids : Partially due to generating some conjugate acids and partially due to weak

Question 32

HA -H+ +A -

Answer 32

Strong acid conjugate base
Strong acids will readily loose a proton meaning its conjugate base is very stable weak base it doesn’t want a proton

high concentration of H+

Question 33

HA - H+ + A -

Answer 33

Weak acid , Strong base

The acid does not want to loose the proton it will have a strong conjugate base in which it will easily gain an proton .