C. LONG ANSWER TYPE QUESTIONS
1. Mention two characteristics of each acids, bases and indicators.
2. How is litmus obtained ? How would you use a litmus paper to differentiate the given solutions of
dilute hydrochloric acid and ammonium hydroxide ?
3. What are synthetic indicators ? Name the synthetic indicator that turns red into acidic medium.
4. What is an exothermic reaction ? Give an example.
5. Give reason for the following:
(a) The toothpaste prevents tooth decay. (b) Baking soda paste is advised to rub on a bee sting.
Answers
Answer:
Explanation:1=Acids taste sour while bases taste bitter. An acid reacts with metals to produce bubbles of hydrogLitmus paper can be used as an pH indicator to differentiate the acids and bases. Explanation: Litmus paper when placed in acid turns red and base turns blue. When a litmus paper is placed in dilute HCl then it turns red and when placed in ammonium hydroxide the solution nature is revealed.en gas while a base feels slimy to the touch. Acids turn blue litmus paper red while bases turn red litmus paper blue.
2=Litmus paper can be used as an pH indicator to differentiate the acids and bases. Explanation: Litmus paper when placed in acid turns red and base turns blue. When a litmus paper is placed in dilute HCl then it turns red and when placed in ammonium hydroxide the solution nature is revealed.
3=Methyl orange is a pH indicator frequently used in titration because of its clear and distinct color variance at different pH values. Methyl orange shows red color in acidic medium and yellow color in basic medium. Because it changes color at the pKa of a mid strength acid, it is usually used in titration for acids.
4=The bacteria, acid, food debris, and saliva combine to form plaque, which clings to the teeth. The acids in plaque dissolve the enamel surface of the teeth, creating holes in the teeth called cavities. To prevent tooth decay: Brush your teeth at least twice a day with a fluoride-containing toothpaste.
b=A paste made of baking soda and water can help neutralize bee venom to reduce pain, itching, and swelling. Apply a thick layer of baking soda paste to the affected area. Cover the paste with a bandage. Leave on for at least 15 minutes and re-apply as needed.