Why do we have to use 2 indicators in alkalinity?


Why do we have to use 2 indicators in alkalinity?

Water Alkalinity is mainly due to carbonate and bicarbonate salts in a water sample, the carbonate ion has two end points, one from carbonate to bicarbonate and another from bicarbonate to carbon dioxide.

Why do we use different indicators?

Since the color of the indicator depends on the pH of the solution, indicators find wide use in applications that involve pH changes, such as titrations, pH testing, and science demonstrations. The most important property of an indicator is its pH range, which is dependent on the indicator’s acid strength.

What are 2 uses of indicators?

found in Gault (2010), who outlines four ways that indicators are used for policy purposes: monitoring, benchmarking, evaluating, and “foresighting.”

Why both phenolphthalein and methyl orange are used as indicators?

In the case of acid base reaction, chemical indicators like methyl orange or phenolphthalein are used to determine end point. These indicators changes color with the change in the pH of the solution. Reactant/ analyte : It is the solution whose concentration is not known.

What are the 2 indicators used in determination of alkalinity of water?

Alkalinity is measured titrimetrically by titrating against Dilute Sulphuric Acid. Phenolphthalein and Methyl Orange are used as indicator to indicate pH 8.3 and pH 4.3. Phenolphthalein process a pink colour when pH is above 8.3 and colourless when pH is below 8.3.

What is double indicator titration?

In the acid-base titration the equivalence point is known with the help of indicator which changes its color at the end point. In the titration of polyacidic base or polybasic acid there are more than one end point. One indicator is not able to give color change at every end point.

What are the 3 types of indicators?

Indicators can be described as three types—outcome, process or structure – as first proposed by Avedis Donabedian (1966).

What makes a good indicator?

The indicator should be focused, clear and specific. An indicator should be defined in precise, unambiguous terms that describe clearly and exactly what is being measured. Where practical, the indicator should give a relatively good idea of the data required and the population among whom the indicator is measured.

How do we use indicators in everyday life?

Everyday uses of indicators include: Testing the acidity or basicity of soils, as some plants grow best in slightly acidic soils (such as azaleas and pineapples) while others grow best in slightly basic soils (such as violets):

Why is phenolphthalein used?

Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions. Phenolphthalein is slightly soluble in water and usually is dissolved in alcohols for use in experiments.

Why two indicators namely phenolphthalein and methyl orange are selected for determining alkalinity?

Since phenolphthalein changes color at pH~8.3, this corresponds to a pH where all the CO32- present would be protonated. Second, acid titration to a methyl orange end point, pH~4.3, further converts the bicarbonate to aqueous carbon dioxide. The methyl orange end point titration indicates total alkalinity.

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