Question

Which of the following statements is correct?
1. A soil containing chemicals is preferred for manufacturing portland cement
2. A soil having pH value more than 7 is an acidic soil
3. A soil having pH value less than 7 is an acidic soil
4. A soil having pH value more than 7 is an alkaline soil

Answer 1

Correct Answer - Option 3 : A soil having pH value less than 7 is an acidic soil

Explanation:

• Soil can be classified according to its pH values.
• pH value from 7.0 to 7.5 is considered neutral.
• pH value over 7.5 is alkaline.
• pH value less than 7.0 is acidic.
• Soils with a pH less than 5.5 are considered strongly acidic.​​​​

• pH of the pH scale stands for the power of Hydrogen. It consists of the value from 0 to 14.
• The concept of pH was first introduced by the Danish chemist Søren Peder Lauritz Sørensen in1919.
• pH scale in Chemistry is used to determine the acidity or basicity of a solution.
• pH scale indicates the concentration of Hydrogen ions in the solution. 

• Litmus, turmeric, red cabbage, China rose, etc. are some common natural indicators used widely to show the acidic or basic character of substances.

• Litmus is obtained from lichens. The solution of litmus is purple in colour.
• Litmus paper comes in two colours – blue and red. An acid turns blue litmus paper into the red. A base turns red litmus paper into the blue.

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Substance	pH
Rainwater	6.0
Tear	7.4
Urine	4.8-8.4
Sea Water	8.5
Gastric Juice	1.0-3.0
Saliva	6.5-7.5