Question 1

What is the pH value of a neutral aqueous solution at 25°C?

Accepted Answer

7. A pH of 7 represents a neutral solution where hydrogen and hydroxyl ions are equal. Pure water is the most common example of such a neutral substance. The pH scale generally ranges from 0 to 14 to measure acidity or alkalinity.

Question 2

Which acid is predominantly found in lemons and oranges?

Accepted Answer

Citric acid. Citric acid is the primary organic acid found in citrus fruits like lemons. It gives these fruits their characteristic sour taste and acts as a natural preservative. This acid is also widely used as a flavoring agent in the food industry.

Question 3

What color does blue litmus paper turn when dipped in an acidic solution?

Accepted Answer

Red. Acids turn blue litmus paper red due to the chemical reaction with hydrogen ions. This is a standard qualitative test used to identify acidic substances in laboratories. Litmus is a natural dye extracted from lichens.

Question 4

Which of the following is commonly known as 'Milk of Magnesia'?

Accepted Answer

Magnesium hydroxide. Magnesium hydroxide is called Milk of Magnesia because of its milk-like appearance when suspended in water. It is frequently used as an antacid to neutralize excess stomach acid. It is considered a weak base and is safe for medicinal use.

Question 5

Which gas is evolved when a dilute acid reacts with a metal like zinc?

Accepted Answer

Hydrogen. Hydrogen gas is produced when metals react with acids through a displacement reaction. This gas can be identified by the 'pop' sound it makes when a burning splinter is brought near. Most reactive metals follow this general chemical behavior with dilute acids.

Acids & Bases — Set 1