buffers and mobile phases

Question 1

Define pH ?

Answer 1

the concentration of H3O+ ions in a dtemined solution

Question 2

How is something pH 7 ?

Answer 2

H2O dissociates in small amounts but in equal parts of H3O+>[OH-],pH below 7 or acidity

Question 3

How do strong acids and bases ionise in water ?

Answer 3

completely
[H3O+]<[OH-]
pH above 7 or alkaline

Question 4

basic formula of pH?

Answer 4

pH =-log[H+]=log 1/[H+]
pH scale ranges from 0 to 14

Question 5

How does water look at the eqm ?

Answer 5

[H2O+]<–>[H3O+][OH-]
Balance of these products is it dissociation constant (K)

Question 6

Examples of Strong acid ?

Answer 6

HCl (hydrochloric acid)
H2SO4 (sulfuric acid)
HNO3 (nitric acid)
HBr (hydrobromic acid)
HClO4 (perchloric acid)

Question 7

define buffers ?

Answer 7

A system that is capable of absorbing “small variations” of either H+or OH–

Question 8

Whatr are buffers used for ?

Answer 8

as a means of keeping pH solutions at a nearly constant value in a wide variety of chemical applications

Question 9

Define Le chateliers principle ?

Answer 9

used to predict the effect of a change in conditions on chemical equilibria
when a simple sytem, in thermodynamic equilibrium is subjected to change in concentration ,temperature,volume or pressure

Question 10

?Define equivalence point

Answer 10

point in titration at which the amount of titrant added is just enough to completely neutralises the analyte solution.
acid base titration moles of bases =moles of acid and the solution only contains salt and water

Question 11

Typical laborotory buffer ?

Answer 11

Tris
used in biological techniques conjugate acid of about pH 8.7
TBE: Tris/Borate/EDTA
TAE:Tris/acetate/EDTA

Question 12

Some properties of buffers: resolution and conductivity ?

Answer 12

TBE buffer has better buffering capacity than TAE s

Question 13

What is a good laboratory buffer solution ?

Answer 13

1. Buffered pH close to working pH
2. Good solubility of compounds
3. Minimal interactions with compounds and reactions
4. Minimal salt effect
5. Non-toxic for system investigated
6. pKa in range of observed reaction between 6,8
7. solubility in water

Question 14

How to select appropraite buffer ?

Answer 14

1. Minimal salt effects :should not interact or affect ions involved in biochemical reactions being explored
   2.Minmal effects on dissociation from changes in temp and conc
   3.Minimal interactions between buffer components and critical reaction components.
   4.Chelating agent :citrate,EDTA
   5.Buffers are not inert.
   6.Chemical stability.
   7.Light absorption.
   8.Ease of Use.

Question 15

Define Chromatography ?

Answer 15

used to seperate complex mixtures into their constituent components to allow for better anaylsis of these components to allow for better analysis of these components

Question 16

What is the characterisation of natural products ?

Answer 16

1. Drug testing
2. clinical diagnostics
3. Food purity
4. Drug metabolisms

Question 17

Why do we need chromatogrphy ?

Answer 17

biological samples are analytically complex compromising between 00’s and 000’s of small molecules

Question 18

What is seperation by partioning ?

Answer 18

seperation due to partioning between 2 immiscible phases is very important
basis of chromatography methods
solid phase (stationary )
fluid phase (mobile)

Question 19

What is chromatography based on ?

Answer 19

exchange of compound between 2 diff pahses
compund continually moves between the 2 environment many hundreds of time per second