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Biochemistry Laboratory > PH MEASUREMENT AND BUFFER PREPARATION > Flashcards

PH MEASUREMENT AND BUFFER PREPARATION Flashcards

1
Q

measure of how acidic/basic a solution is.

A

pH

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2
Q

0 to 14.

A

range

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3
Q

pH < 7

A

acidic

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4
Q

pH = 7

A

neutral

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5
Q

pH > 7

A

basic

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6
Q

potential of hydrogen

A

ph

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7
Q

measure of the hydrogen ion (H+) concentration in an aqueous solution

A

pH

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8
Q

expressed as the negative logarithm of the hydrogen-ion concentration.
pH = - log [H+]

A

pH

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9
Q

potential of Hydroxide

A

pOH

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10
Q

measure of hydroxide ion (OH-) concentration

A

pOH

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11
Q

expressed as the negative logarithm of the hydroxide-ion concentration.
pOH = - log [OH-]

A

pOH

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12
Q

important in organism and their cells because chemical reactions and processes are affected by the hydrogen ion concentration.

A

control of pH

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13
Q

requires a pH between 7.8 and 8.4

A

Nemo (Clownfish)

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14
Q

compound that can donate a hydrogen ion.

A

acid

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15
Q

substance that accepts hydrogen ions.

A

base

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16
Q

Hydrogen ions
low ph/ many hydrogen ions

A

ACIDS

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17
Q

(hydroxide ions)
high ph/ many hydroxide ions

A

ALKALIS

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18
Q

Chemists have tried to define acids and bases in relation to their compositions and molecular structures.

A

Background

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19
Q

defines acids as substances that produce H+ ions in aqueous solution while bases are substances that produce OH- ions in aqueous solution.
Pronounced as “svaan-tay”

A

Svante Arrhenius

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20
Q

Mentioned that acids are electron-pair acceptors and bases are electron-pair donor.
However, the two mentioned definitions have limitations. Thus, the most useful and accepted definition of acids and bases nowadays are those proposed by Johannes Bronsted and Thomas Lowry, and it is known as the Bronsted-Lowry theory.

A

Gilbert N. (G.N.) Lewis

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21
Q
  • HCI (Hyrochloric acid) is an acid because it donates a proton making Cl- (Chloride) while water is a base because it accepts a proton making H30+.
  • Furthermore, the theory explains that for every acid-base reaction, there is a creation of conjugate acid-base pair.
  • In the above example Cl- is the conjugated base of HCl and H30+ is the conjugated acid of water as shown below.
A

Rationale:

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22
Q

introduced the pH scale that measures the strength of an aqueous acidic or basic solution.
It converts the H+ concentrations to pH using the formula.
pH = - log [H+]

A

Seren Peter Lauritz Sorensen
(S.P.L.) Sorensen

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23
Q

is “the negative common logarithm of the activity of hydrogen ion in solution

A

precise definition of pH

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24
Q

The pH of a solution is the negative logarithm of the hydrogen-ion concentration.
pH = -log|H+]

A

Computation of pH & [H+]

25
Q

compute for the pH of pure water with [H+] = 1.0 × 10 -7 M (Molarity).

A

pH = -log|H + ]
= - 10g|1.0 × 10 -7]
= -(-7.00)
pH = 7.00

26
Q

compute for the pH of pure water with [H+] = 1.0 × 10 -7 M (Molarity).

A

pH = -log|H + ]
= - 10g|1.0 × 10 -7]
= -(-7.00)
pH = 7.00

27
Q

Compute for the pH of solution with [H+] = 2.3 × 10-5 M

A

pH = -log[H + ]
= - 10g|2.3 × 10 -5]
pH = 4.64 (Acidic)

28
Q

compute for the [H+] if pH is known using this formula:

A

[H+] = 10^-рН
*Use the 10^x key on your calculator

29
Q

What is the [H+] of a solution with a pH of 9.14?

A

[Н+] = 10^-рН
= 10^-9.14
[H+] = 7.24 × 101-10 M

30
Q

What is the [H+] of a solution with a pH of 5.4?

A

[H+] = 10^-pH
=101-5.4
[H+] = 3.98 × 101-6 M

31
Q

The pOH of a solution is the negative logarithm of the hydroxide-ion concentration.
рОН = -log[OH-]
[ОН-] = 10^-рОН
*Use the 10^x key on your calculator
Constant: pH + pOH = 14

A

Computation of poH

32
Q

The pOH of a solution is the negative logarithm of the hydroxide-ion concentration.
рОН = -log[OH-]
[ОН-] = 10^-рОН
*Use the 10^x key on your calculator
Constant: pH + pOH = 14

A

Computation of poH

33
Q

A solution has a pH of 4. Find the pOH and [OH-].

A

pH + pOH = 14
рОН = 14 - рН рОН = 14 - 4
рОН = 10

[ОН-] = 10^-рОН
= 10^-10
[OH-] =1 × 10^-10 M

34
Q

Find the pOH and [OH-] of a solution with a pH of 8.4.

A

pH + pOH = 14
рОН = 14 - рн рОН = 14 - 8.4
рОн = 5.6

[ОН-] = 10^-рОН
= 10^-5.6
[OH-] = 2.5 × 10^-6 M

35
Q

If pH > 7 = Basic
, <7 = Acidic
If pOH >7 = Acidic
, <7 = Basic
7 = Neutral

A

Interpretation of Results

36
Q

prevent changes in pH.

A

Buffers

37
Q

resist changes in the pH even when acids or bases are added.

A

Buffers

38
Q

are a mixture of a weak acid or alkali and one of its salts. Ex: acetic acid + sodium acetate

A

Buffers

39
Q

The ability of buffers to resist large changes in pH is governed by

A

Le Chatellier’s principle.

40
Q

A principle of equilibrium shift due to changes in buffer conditions.

A

La Chatellier’s Principle

41
Q

In our blood, carbonic acid is the most important buffer.
This solution maintains our blood pH to facilitate transport of oxygen from the lungs to the cells.

A

Buffers in Human Blood

42
Q

normally slightly basic (7.35 to 7.45)

A

pH of blood

43
Q

simple test to check if a substance is acidic or basic using a litmus paper.

A

Litmus Test

44
Q

types of litmus paper available that can be used to identify acids and bases

A

red litmus paper and blue litmus paper

45
Q

turns red for acidic pH

A

Blue litmus paper

46
Q

turns blue for basic pH

A

Red litmus paper

47
Q

No color change

A

neutral pH

48
Q

impregnated with organic compounds that change their color at different pH values.
The color shown by the paper is then compared with a color standard usually provided by the manufacturer.

A

Indicator Paper

49
Q

impregnated with organic compounds that change their color at different pH values.
The color shown by the paper is then compared with a color standard usually provided by the manufacturer.

A

Indicator Paper

50
Q

should be calibrated first before being operating the device. The standard procedure for calibrating a pH meter is to calibrate it at three different pHs (pH 7, pH 4, and pH 10).
After calibration, all that needs to be done is to insert the electrodes of the pH meter into the solution to be tested and read the pH flashed on the screen.

A

pH Meter

51
Q

an indicator that can be used to determine the pH value of a solution

A

pH PAPER

52
Q

an indicator that is used to determine the acidity or the basicity of a solution

A

LITMUS PAPER

53
Q

Can give the exact pH value of a solution

A

pH PAPER

54
Q

Cannot give the exact pH value of a solution

A

LITMUS PAPER

55
Q

Give more precise results

A

pH PAPER

56
Q

Give a less precise indication

A

LITMUS PAPER

57
Q

Can give a range of colors

A

pH PAPER

58
Q

Can give only two colors

A

LITMUS PAPER

Biochemistry Laboratory (4 decks)

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