Acids , Bases Some Important Questions & Answers For 10th Board Exam.

 VIVA VOCE QUESTIONS 

1. what are acids?
Ans. Acids are the substances which give hydrogen ions (`H^+` ions) in aqueous solutions.
2. what are bases? 
Ans. Bases are the substances which give hydroxyl ions (`OH^-`ions) in aqueous solutions.
3. Give any two examples of acids.
Ans. Hydrochloric acid (HCL) and sulphuric acid (`H_2SO_4`).
4. Give two examples of bases.
Ans. Sodium hydroxide (NaOH) and potassium hydroxide (KOH).
5. Name the acid present in vinegar.
Ans. Acetic acid (`CH_3COOH`).
6. Name the acid present in lemon juice.
Ans. Citric acid 
7. What do you understand by pH?
Ans. pH of a solution is a measure of the concentration of hydrogen ions in the solution. Knowing the pH , we can tell whether the solution is acidic, basic or neutral.  
8. Define pH. 
Ans. pH of a solution is defined as the negative logarithm of the concentration of hydrogen ions in moles per litre.
              pH = -log [`H^+`]
 9. What is the normal range of pH? 
 Ans. 0 to 14. 
10. What is the pH of neutral solution at 25°C?
 Ans. The pH of neutral solution is 7 at 25°C. 
11. A solution has pH equal to 6. Will it be acidic, basic or neutral? 
Ans. It will be acidic. 
12. What is the pH of a solution having hydrogen ion concentration `10^{-3}` moles per litre? 
Ans. 3 
13. What is the pH of pure water at 298 K? 
Ans. 7
14. An aqueous solution of hydrochloric acid is diluted with water. What happens to the pH of the solution? 
Ans. The pH of the solution increases due to decrease in the concentration of `H^+` ions. 
15. An aqueous solution of sodium hydroxide is diluted with water. What happens to the pH of the solution? 
Ans. The pH of the solution decreases due to decrease in the concentration of `OH^-` ions and the corresponding increase in the concentration of `H^+` ions.
16. What is the pH of an aqueous solution of ammonia? 
Ans. The pH of aqueous solution of ammonia would be more than 7 as the solution is basic in nature. 
17. Name any two acid base indicators. 
Ans. Phenolphthalein and methyl orange. 
18. What is the colour of litmus solution in an acidic solution?
Ans. Red
19. What is the colour of phenolphthalein in a basic solution and in an acidic solution? 
Ans. The colour is pink in basic solution and colourless in acidic solution.
20. What is universal indicator solution? 
Ans. Universal indicator solution is a solution which has different colours at different pH values. It is a mixture of a number of indicators. 
21. What is the pH of fluids in our stomach? 
Ans. The pH of fluids in our stomach is nearly equal  to 2.
 22. Name the acid present in the fluids in our stomach. 
Ans. Hydrochloric acid. 
23. What is the pH of soap solution? 
Ans. pH of soap solution is greater than 7. 
24. What is the pH of human blood? 
Ans. Approximately 7.4
25. What is the colour of universal indicator solution in a strongly acidic solution?
 Ans. Red 
26. What is the colour of universal indicator solution in a strongly basic solution? 
Ans. Blue-violet 
27. What is the colour of methyl orange in sodium hydroxide solution? 
Ans. Yellow 
28. What do you understand by the term hyperacidity? 
Ans. It is the term used for the condition when we have excess of acidity in our stomach. 
29. A few drops of methyl orange are added to vinegar. What would be the colour of the solution? 
Ans. Red, because the solution is acidic. 
30. What is an antacid? 
Ans. It is a medicine used to cure hyperacidity. 
31. Name any two antacids.  
Ans. Sodium bicarbonate and milk of magnesia. 
32. Name the acid present in curd.
 Ans. Lactic acid 
33. How does the pH of milk change as it turns into curd? 
Ans. The pH of milk decreases as it changes into curd due to formation of lactic acid.

    NCERT LAB MANUAL QUESTIONS

1. What is the pH of pure water at 25°C (298 K)?
 Ans. The pH of pure water is 7 at 25°C. 
2. What according to you should be the pH of dil. HCl and dil. NaOH solutions? Observe and explain your findings. 
Ans. The pH of dilute HCl should be less than 7. For a dil. HCl solution having conc. 0.01 M (M/100), the pH would be approximately 2. 
The pH of dil. NaOH solution should be more than 7. For a dil. NaOH solution having conc. 0.01 M (M/100), the pH would be equal to 12. 
3. On opening the soda water bottle the dissolved `CO_2` comes out. Would the pH of the solution increase or decrease as the gas comes out? Explain your answer either way. 
Ans. `CO_2` in dissolved form exists as carbonic acid (`H_2CO_3`). On opening the soda water bottle, the dissolved `CO_2` comes out resulting in the decrease in concentration of carbonic acid. Hence, the pH of the solution increases.