Acids Bases and Salts
1. A solution turns red litmus blue, its pH is likely to be
(a) 1 (b) 4 (c) 5 (d) 10
2. A solution reacts with crushed egg-shells to give a gas that turns lime-water milkey. The solution contains
(a) NaCl (b) HCl (c) LiCl (d) KCl
3. 10 mL of a solution of NaOH is found to be completely neutralized by 8 mL of a given
solution of HCl. If we take 20 mL of same solution of NaOH, the amount of HCl solution required to neutralize it will be
(a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL
4. Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotics (b) Analgesic (c) Antacid (d) Antiseptic
5. Write word equations and then balanced equations for the reaction taking place when:
(a) Dilute Sulphuric acid reacts with zinc granules.
(b) Dilute hydrochloric acid reacts with magnesium ribbon.
(c) Dilute Sulphuric acid reacts with aluminum powder
(d) Dilute hydrochloric acid reacts with iron fillings.
6. Compound such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity.
7. Why does distilled water not conduct electricity, where as rain water does?
8. Why do acids not show acidic behavior in the absence of water?
9. Five solutions A, B, C, D and E when tested with universal indicators showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is:
(a) Neutral? (b) Strongly alkaline?
(c) Strongly acidic (d) Weakly acidic ?
(e) Weakly alkaline
10. Equal lengths of magnesium ribbons are taken in test tubes A and B. hydrochloric acid is added to test tube A, while acetic acid is added to test B. In which test tube will the fizzing occur more vigorously and why?
11. Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
12. A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the milk from 6 to slightly alkaline?
(b) Why does this milk take a long time to set a curd?
13. Plaster of Paris should be stored in moisture-proof container. Explain why?
14. What is a neutralization reaction? Give two examples.
15. Give two important uses of washing soda and baking soda.
16. You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus solution, how will you identify the contents of each test tube?
17. Why should curd and sour substance not be kept in brass and copper vessels.
18. Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
19. Metal compound ‘A’ reacts with dilute hydrochloric acid to produce efferenvescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction, if one of the compounds formed is calcium chloride.
20. Why do HCl, HNO3 etc. show acidic characters in aqueous solution while solutions of compounds like alcohol and glucose do not show acidic character?
21. Why does an aqueous solution of an acid conduct electricity?
22. Why does dry HCl gas not change the colour of the dry litmus paper?
23. While diluting an acid, why it is recommended that the acid should be added to water and not water to the acid?
24. How is concentration of hydronium ions (H30+) affected when a solution of acid is diluted?
25. How is concentration of hydroxide ions (OH–) affected when excess base is dissolved in a solution of sodium hydroxide?
26. You have two solutions ‘A’ and 13′. The pH of solution ‘A’ is 6 and pH of solution ’13’ is 8. Which solution has more hydrogen ions concentration? Which is acidic and which one is basic?
27. What effect does the concentration of H+ ions have on the nature of the solution?
28. Do basic solutions also have H+ ions? If yes, then why are these basic?
29. Under what soil condition do you think a farmer would treat the soil of his field with quicklime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate).
30. What is the common name of the compound CaOC12?
31. Name the substance which on treatment with chlorine yields bleaching powder.
32. Name the sodium compound which is used for softening hard water.
33. What will happen if a solution of sodium hydrogen carbonate is heated? Give the equation of reaction involved.
34. Write an equation to show the reaction between plaster of Paris and water.