Acids - Properties and Examples - UNSOLVED PRACTICE SET

Q7. Define an acid. Classify acids into mineral acids and organic acids, giving two examples of each.

Q8. Write the chemical formulae of the following acids: (i) Hydrochloric acid, (ii) Sulphuric acid, (iii) Nitric acid, (iv) Acetic acid.

Q9. Your grandmother uses tamarind (imli) while cooking dal. She says it adds a tangy flavour. What type of substance is tamarind? Name the acid present in it and explain why it tastes sour.

Q10. Why are mineral acids called "mineral acids"? Give two examples and mention one use of each.

Q11. Distinguish between a strong acid and a weak acid with one example of each. How does their behaviour with water differ?

Q12. Why should you never taste or touch acids directly in the laboratory, even though some acids like citric acid are present in food we eat?

Q13. Define acids and describe their general properties. Explain the difference between mineral acids and organic acids with at least three examples of each. Why do acids taste sour? Write the ionisation equation of hydrochloric acid in water.

Q14. A student is given four unlabelled bottles containing the following solutions: dilute HCl, lemon juice, vinegar, and dilute H₂SO₄. She has blue litmus paper, red litmus paper, and a piece of zinc metal. Help her identify the acids by:

(a) Explaining what happens when each solution is tested with blue litmus paper.

(b) Describing what happens when zinc is added to each solution.

(c) Explaining how she can distinguish between the two mineral acids (HCl and H₂SO₄).

(d) Suggesting one additional test to confirm the presence of HCl specifically.

Q15. "Acids are both friends and foes in our daily lives." Discuss this statement by explaining: (i) beneficial uses of acids in food, medicine, and industry, (ii) harmful effects of strong acids on human health and the environment, (iii) the role of acids in digestion, and (iv) why acid rain is a serious environmental concern in industrial cities of India.

Q16. A chemistry teacher prepares dilute solutions of acids for a class demonstration:

(a) She dissolves 7.3 g of HCl gas in water to make 200 mL of solution. Calculate the molarity of the solution. (Molar mass of HCl = 36.5 g/mol)

(b) If she takes 10 mL of this solution and dilutes it to 100 mL, what is the new molarity?

(c) Vinegar contains approximately 5% acetic acid (CH₃COOH) by mass. If a bottle contains 500 g of vinegar, calculate the mass of acetic acid present.

(d) If the density of vinegar is approximately 1 g/mL, calculate the molarity of acetic acid in vinegar. (Molar mass of CH₃COOH = 60 g/mol)

Q17. In a school laboratory, students test various household substances to identify acids:

Table

Substance Test with Blue Litmus Test with Red Litmus Reaction with Zinc

A Turns red No change Bubbles form

B No change Turns blue No reaction

C Turns red No change Bubbles form

D No change No change No reaction

(a) Identify which substances are acidic, basic, and neutral.

(b) Substances A and C both react with zinc. How can you distinguish between a strong acid and a weak acid using the rate of bubbling?

(c) If substance A is dilute HCl and 0.73 g of HCl is present in 100 mL, calculate its molarity.

(d) Substance D is distilled water. Why does it not change the colour of either litmus paper?

Q18. A fruit juice manufacturer in India produces packaged mango juice and orange juice.

(a) Mango juice contains citric acid, while orange juice contains both citric acid and ascorbic acid (Vitamin C). Write the chemical formulae of these acids.

(b) If a 250 mL pack of orange juice contains 60 mg of Vitamin C (C₆H₈O₆), calculate the molarity of Vitamin C in the juice. (Molar mass of Vitamin C = 176 g/mol)

(c) The manufacturer adds citric acid as a preservative. If 1.2 g of citric acid (C₆H₈O₇) is added per litre, calculate the number of moles of citric acid in a 500 mL pack. (Molar mass of citric acid = 192 g/mol)

(d) Why do fruit juices taste sour? Explain in terms of hydrogen ion concentration.

(e) The manufacturer tests the pH of the juice and finds it to be 3.5. Calculate the hydrogen ion concentration [H⁺].