Explain why there is an uncertainty in pH values that are measured using universal indicator.

Please help!!

The chemical properties of many solutions enable them to be divided into three categories - acidic, alkaline and neutral solutions.

The pH scale is used to measure acidity and alkalinity:

solutions with a pH less than 7 are acidic

solutions with a pH of 7 are neutral

solutions with a pH greater than 7 are alkaline

If universal indicator is added to a solution it changes to a colour that shows the pH of the solution. Universal indicator is a mixture of a variety of other indicators and can be used to measure the approximate pH of a solution. A more accurate value can be obtained using a pH probe.

A coloured pH scale, ranging from dark red at pH 0, orange at pH 3, green at pH 7, blue at pH 10 to dark purple at pH 14.

pH scale and universal indicator colours

The chemical properties of many solutions enable them to be divided into three categories - acidic, alkaline and neutral solutions.

The pH scale is used to measure acidity and alkalinity:

solutions with a pH less than 7 are acidic

solutions with a pH of 7 are neutral

solutions with a pH greater than 7 are alkaline

If universal indicator is added to a solution it changes to a colour that shows the pH of the solution. Universal indicator is a mixture of a variety of other indicators and can be used to measure the approximate pH of a solution. A more accurate value can be obtained using a pH probe.

A coloured pH scale, ranging from dark red at pH 0, orange at pH 3, green at pH 7, blue at pH 10 to dark purple at pH 14.

pH scale and universal indicator colours

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.