Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Acids are substances that taste sour and turn blue litmus paper red. They contain hydrogen ions ().
Bases are substances that taste bitter, feel soapy to the touch, and turn red litmus paper blue. They contain hydroxyl ions ().
Neutral substances are neither acidic nor basic and do not change the color of indicators (e.g., pure water, common salt solution).
Indicators are special substances used to test the acidic or basic nature of a solution. Natural indicators include litmus (extracted from lichens), turmeric, and China rose petals.
Phenolphthalein is a synthetic indicator: it remains colorless in acidic solutions and turns deep pink in basic solutions.
The reaction between an acid and a base is called a neutralization reaction, resulting in the formation of salt and water along with the evolution of heat.
Organic acids like Citric acid () are found in citrus fruits, while Lactic acid is found in curd.
Mineral acids like Hydrochloric acid () and Sulfuric acid () are highly corrosive and used in laboratories.
📐Formulae
💡Examples
Problem 1:
What is the chemical reaction when Hydrochloric acid reacts with Sodium hydroxide?
Solution:
Explanation:
This is a neutralization reaction where the acid () and base () react to form Sodium Chloride (), which is a neutral salt, and water ().
Problem 2:
How is indigestion treated using chemistry?
Solution:
Explanation:
Our stomach contains for digestion. Excess acid causes indigestion. We take an antacid like Milk of Magnesia, which contains Magnesium hydroxide (), a base that neutralizes the excess acid.
Problem 3:
What happens chemically when an ant bites?
Solution:
The ant injects Formic acid (). It is neutralized by rubbing moist baking soda (Sodium hydrogen carbonate, ):
Explanation:
The acidic effect of the ant sting is neutralized by the basic nature of baking soda or calamine solution (Zinc carbonate).