Slide 1 : WELCOME
pH VALUE : pH VALUE .
What is PH? : What is PH? In chemistry, pH is a measure of the acidity or basicity of a solution.
Slide 4 : The concept of pH was first introduced by Danish chemist Soren Peter Lauritz Sorensen at the Carlsperg Laboratory in 1909,defining it as pH = -log[H+],i.e; the negative logarithm of hydrogen ion concentration.
DEFINITION OF pH : DEFINITION OF pH The quantity pH is defined as the negative logarithm of the hydronium ion concentration in mols per litre
Mathematical Definition
pH=-log10[H3O+]
or
pH=log101/[H30+]
pH VALUE OF WATER : pH VALUE OF WATER In water, [H30+]=[OH-] = 1*10-7 mol l-1 at 298 K
Therefore, pH= -log[H30+] =-log(1*10-7)=7 Thus Pure water is said to be neutral, with a pH close to 7.0 at (25 oC).
NEUTRAL,ACIDIC & BASIC : NEUTRAL,ACIDIC & BASIC When pH is equal to 7, the solution is neutral. When it is above 7, the solution is basic and when it is below 7, the solution is acidic. pH=7 pH=8 pH=3
Slide 8 : pH measurements are important in medicine ,biology ,chemistry , food science , environmental science, oceanography and many other applications.
MEASUREMENT OF pH : MEASUREMENT OF pH pH can be measured using either pH indicators ( in form of solution ) or pH strips or using potentiometric method.
pHSCALE : pHSCALE
pH INDICATORS : pH INDICATORS An approximate measure of pH may be obtained by using a pH indicator. A pH indicator is a substance that changes colour around a particular pH value that can be determined visually. It is a weak acid (phenolphthalein) or weak base(methyl orange). pH indicators are frequently employed in titrations, in analytic chemistry and in biology experiments to determine the extent of a chemical reaction.
Acid-Base Indicators : Phenolphthalein
Acid-colourless
base-pink
pH =8-9.8
Methyl orangeacid-orangebase-red
pH =3.1-4.5 Acid-Base Indicators
pH PAPERS : pH PAPERS Strips are very useful when all you need is 0.2-0.5 pH unit accuracy.
pH strips are nothing else but pieces of paper impregnated with indicator or a mixture of indicators .
For example, the litmus paper is red in acidic solutions and blue in alkaline solutions.
pH meter : pH meter A pH meter is an electronic instrument used to measure the pH of a liquid .A typical pH meter consists of a special measuring probe (a glass electrode) connected to an electronic meter that measures and displays the pH reading.
UNIVERSAL INDICATOR : UNIVERSAL INDICATOR The universal Indicator was invented in 1923 by Yamada.
It consists of a mixture of indicators such that there is a continuous colour change from about pH 2 to pH 10. is
COMPOSITION OF UNIVERSAL INDICATOR : COMPOSITION OF UNIVERSAL INDICATOR A universal indicator is typically composed of water, methanol, propan-1-ol, phenolphthalein sodium salt, methyl red sodium salt, phenol,4,4'-(3h-2,1-benzoxathiol-3-ylidene)bis2-bromo--methyl -6-(1-methylethyl)-, s,s-dioxide, monosodium salt, and phenol,4,4'-(3h-2,1-benzoxathiol-3-ylidene)bis5-methyl2-(1-methyl ethyl)-, s, s-dioxide, monosodium salt.
UNIVERSAL INDICATOR PAPER : UNIVERSAL INDICATOR PAPER 1. Very acidic - Red 2. Acidic - Orange/Yellow 3. Neutral - Green 4. Basic/base/alkali - Blue 5. Very basic/base/alkali - Purple
NATURALLY OCCURING pH INDICATORS : NATURALLY OCCURING pH INDICATORS pH-dependent plant pigments that can be used as pH indicators occur in many plants, including hibiscus, marigold, red cabbage and red wine. Hydrangea macrophylla blossoms are either pink or blue depending on soil acidity(pink in basic and blue in acidic).
MAKING OF A NATURAL pH PAPER : MAKING OF A NATURAL pH PAPER Anthocyanin extract
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Slide 21 : THANK YOU