Class – 10

ACID BASES & SALT

NCERT SOLVED QUESTION & ANSWER

A. Question Carry one marks

1. Name the gas formed when sodium hydroxide reacts with zinc.

2. Write the chemical name of baking soda.

3. What happens when gypsum is heated at 373K?

4.Why does tooth decay start when the pH of mouth is lower than 5.5?

5. What is baking powder? How does it make the cake soft and spongy?

6. Fresh milk has a pH Of 6. When it changes to curd, will its pH value increase or decrease?.Why

7. Arrange in the increasing order of their pH values: NaOH solution, Blood, Lemon juice,

8. Two solutions A and B have pH values of 5 and 8 respectively. Which solution will be basic in nature?

9. Why does an aqueous solution of acid conduct electricity?

10. Plaster of Paris should be stored in a moisture-proof container. Explain why?

B. Question carry two marks

1.What happens to the crystals of washing soda when exposed to air?

2. What is the chemical name of washing soda? Name three raw materials used in

making washing soda by Solvay process?

3. How is sodium hydrogen carbonate from a mixture of NH4Cl and NaHCO3 ?

4. Give the Names of Raw Materials that are required for the manufacture of washing soda by solvay process. Write the reactions involved in the process.

5. What is efflorescence? Name one compound which shows efflorescence? support your answer with reaction?

6. why is calcium sulphate hemihydrate called ‘Plaster of Paris’ ?

7. Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH3COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?

8. Question: A few drops of phenolphthalein indicator was added to an unknown solution A. It acquired pink color. Now another solution B was added to it drop wise and the solution ultimately became colorless. Predict the nature of the solution A and B.

9. Explain why? (a) Common salt becomes sticky during the rainy season. (b) Blue vitriol changes to white upon heating.

C. Question carry three marks

1. What compound is plaster of peris ? how is it prepared ?what happen when it is mixed with water and allowed to stand ?mention two properties of plaster of peris.

2. Five solution A,B,C,D and E when tested with universal indicator showed PH as 4,1,11,7 and 9 respectively. which solution is (a) neutral (b) strongly alkaline (c)strongly acid (d) weakly acid  and (e) weakly alkaline, arrange the pH in increasing order of H-ion concentration.

3. (a) An aqueous solution has a PH value of 7.0. Is this solution acidic, basic or neutral?

    (b) If H+ concentration of a solution is 1´10-2mol L-1what will be its P4 value?

    (c) Which has higher PH value: 1-M HCl or 1-M NaOH

4. What will you observe when:

      (i) Red litmus is introduced into a solution of sodium sulphate.

      (ii) Methyl orange is added to dil HCl.

     (iii). Blue litmus is introduced into a solution of ferric chloride

5. a) define  an acid-base indicator.mention one acid and base-indicator

    b) if some one in family suffering from a problems of acidity after over eating, which of the following substances would you suggest as a remedy ?.lemon juice ,vinegar or baking soda solution.mention the property on the basis of which you will choose the remedy.

6.(a)three acidic solution A,B and C have PH value 0,3, and 5 respectively

          (i) which solution has highest concentration of  H+ ions solution

          (ii) which solution has lowest  concentration of  H+ ions solution

   (b)how concentrated sulphuric acid can be diluted? Describe the process

7. What is Bleaching powder? How is it prepared and write its two uses.

8. What happens when

          (a) Solid sodium hydrogen carbonate is heated,

          (b) Chlorine gas is passed through dry slaked lime,

          (c) Gypsum is heated to a temperature of 373 K?

9. How can washing soda be prepared from baking soda ? name an industry use of washing soda other than washing clothes.

D. Question carry five marks

1. (a) The PH of rain water collected from two cities A and B was found to be 6 and 5 respectively. Water of which city is more acidic? Find out the ratio of hydrogen ion concentration in the two samples of rain water?

(b) Arrange the following in order (ascending) of their P4 values. NaOH solution, Blood, lemon Juice

2.  (a) Why does an aqueous solution of acid conduct electricity?

     (b) How does the concentration of hydrogen ions [H 3O +] changes when the solution of     an acid is diluted with water?    

     (c) Which has higher pH.A concentrated or dilute solution of HCl?

     (d) What would you observe on adding dil HCL acid to

                      (i) Sodium bicarbonate placed in a test tube.

                       (ii) Zinc metal in a test tube.

3.a compound which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water. Identify the compound. Write the chemical equation for its preparation. For what purpose is it used in hospitals?

4.(a) illustrate an activity to investigate whether all compounds containing hydrogen are acidic.

   (b) What happen when hydrochloric acid and sodium hydroxide are dissolved in water. Explain giving equation of each.