pH Solution in Laboratory
a.
The measurement of pH by Using Acid-Base
Indicator Solution
Acid-base indicator solution or pH indicator
can be used to calculate pH value. The color change in acid-base indicator
depends on the pH value. The following table is shown the change color acid-base indicator.
For example is phenolphthalein. At pH<8,
phenolphthalein is colorless, whereas at pH 8-10, phenolphthalein is pink. If
phenolphthalein is added by a solution, the color solution changes into red. If
pH>10, the color turns back into colorless.
Acid-base
indicator solutions cannot determine pH value exactly, but it can only predict
the range of pH. Acid-base indicators are very useful in the determination of
acid-base titration final point.
b.
The measurement of pH by Using Universal
Indicator
pH
measurement using universal indicator can determine pH in solution exactly. Two
kinds of universal indicators used are solution indicator and paper indicator.
Measuring pH by using universal indicator is very easy. Drop a sample solution
into universal indicator solution or dip indicator paper into a sample
solution. The color resulted is then compared to the standard color shown at
the indicator table.
Universal Indicator
c.
The measurement of pH by using pH meter
To get
pH value accurately, you can use pH meter. pH measurement by using pH meter is
not difficult. After switching the pH meter on, dip the pH electrode into the
sample solution. Look at the pH value at the monitor of pH meter. After you
finish, wash the electrode bar of the pH meter with aquadesh. To get more
accurate measurement, pH measurement of the same solution is done three times.
pH-meter
