Identification of the Acidic, Basic, Neutral Nature of the Salt Solutions

Our Objective

To study the acidic basic and neutral nature of the salt using litmus test.

The Theory

The pH level of a solution determines whether a solution is acidic, neutral, or basic, which is a common task in chemistry labs.  There are ways to figure out what type of solution you have, depending on your laboratory's equipment and methods. One of the methods is litmus test.

Chemistry Behind pH

A pH scale is a tool for determining the concentrations of acids and bases. The scale runs from 0 to 14, with 0 being the lowest and 14 being the highest. Litmus paper is a test that determines whether a substance is acidic or basic. The paper's colour corresponds to the numbers on the pH scale, indicating the type of substance being tested. pH is defined as the negative logarithm (base ten) of hydrogen ion concentration in moles/ litre.

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Litmus Test

Litmus is the most widely used natural indicator. Lichens are used to make it.  distilled water, it has a mauve (purple) colour. It turns red when added to an acidic solution and blue when added to a basic solution. Litmus paper is available in the form of a solution or strips of paper.

Litmus paper comes in two colours: red and blue. You can use litmus paper to determine the pH of your solution . When a drop of a solution is placed on litmus paper, the colour of the paper changes depending on the pH of the solution. Once the colour changes, you can find the pH by comparing it to the colour chart on the paper's package.

Caution: To be safe, use gloves, eye protection, and work under a fume hood when working with unknown solutions.

Indicators

An indicator is a type of 'dye' that changes colour when it comes into contact with acids and bases. In terms of colour change, this tells us whether the substance we're testing is an acid or a base.

Litmus, Methyl orange, and Phenolphthalein are the three most common indicators for testing acids and bases.

Indicator Colour in acid(pH < 7) Colour at pH = 7 Colour in base(pH > 7)
Red cabbage water Red, pink Purple Blue,green,yellow
Turmeric water Yellow Yellow Red
Phenolphthalein Colourless Colourless Pink,red
Red litmus Red Red Blue
Blue litmus Red Blue Blue
Universal indicator Red, orange, yellow Green Blue, violet, purple

Learning Outcomes

  1. Based on the chemical reactions presented, students comprehend terms such as acids and bases.
  2. Based on the skills learned, the student will be able to analyse and classify the given samples as acids, bases and neutral in the future.
  3. Students learn how to safely handle acids and bases in the laboratory.
  4. Students gain a general understanding of the common requirements for conducting this experiment as well as how to set up the lab for it.