ACIDS, BASES AND SALTS – 2020 Important Questions

1 MARK QUESTIONS 

Q1. What is the pH of gastric juice,  which is released during  digestion?

Q2. A student has four samples  A, B, C, D containing dil. HCI, aqueous KCI, dil. NaOH and distilled water respectively. Which two samples would show an equal value of pH?

Q3. How does a strong acid differ from a concentrated acid?

Q4. Name three chemicals in which common salt used  as the raw material.

Q5. Which gas would be evolved, if sodium bicarbonate is treated with tartaric acid?

Q6. Name two crystalline substances which do not contain water of crystallisation.

Q7. Name the acid present in ant sting.

Q8. Which gas is usually liberated when an acid reacts with a metal?

Q9. Why does tooth decay start when the pH of mouth is lower than 5.5?

Q10. Name a salt which does not contain water of crystallisation.

Q11. Why is tartaric acid added into baking soda to get baking powder?

Q12. How does the concentration of H3O+ ions get affected, when a solution of an acid is diluted?

Q13. Why does dry HCI not change the colour of dry litmus?

Q14.  What happens when nitric acid is added to an eggshell?

Directions (Q. Nos. 15-19)  In the following questions a statement of Assertion is followed by a statement of Reason. Mark the correct choice as

(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.               ·

(b) If both Assertion and Reason are true but Reason is not the correct -explanation of Assertion.

(c) If Assertion is true but Reason is false.

(d) If Reason is true but Assertion is false.

(e). If both Assertion and Reason are false.

Q15. Assertion: Acetic acid does not act as an acid in benzene solution.

            Reason: Benzene is non-polar.

Q16. Assertion: Calcium oxide is a base but not an alkali.

           Reason: Calcium oxide is insoluble in water.

Q17. Assertion: There is no change in the colour of litmus paper when brought in contact with distilled water.

            Reason: Litmus Paper is used to find whether an solution is Acidic or Basic.

Q18. Assertion: When bleaching power is left in the open, its colour changes from blue to white.

            Reason: The change in colour as oxygen breaks away from the compound.

Q19. Assertion: Sodium and Potassium is kept inside kerosene.

           Reason: Sodium does not react with organic solvents like kerosene.

Q20. What is the common name of CaOCl2 ?

(a) Bleaching powder       

(b) Baking soda

(c) Washing soda              

(d) Lime water

Q21.  Which one will turn red litmus blue?

(a) Vinegar                        

(b) Lemon juice

(c) Soft drinks                   

(d) Baking soda solution

Q22.  Among sulphurous acid and sulphuric acid, which is stronger?

(a) Sulphurous acid is stronger than Sulphuric Acid

(b) Sulphuric Acid is stronger than Sulphurous acid.

(c ) Sulphuric Acid and Sulphurous acid are equal in strength.

(d) Dilute Sulphuric Acid is stronger than dilute Sulphurous acid.

3 MARK QUESTIONS 

Q1.  How the following substances will dissociate to produce ions in their solutions?

(i)    Hydrochloric acid

(ii)   Nitric Acid

(iii)  Sulphuric acid

(iv)  Sodium hydroxide

(v)   Potassium hydroxide

(vi)  Magnesium hydroxide             

Q2.  What is tooth enamel chemically? State the condition when it starts corroding. What happens when food particles left in the mouth after eating degrades? Why do doctors suggest use of tooth powder/ toothpaste to prevent tooth decay?

Q3. State  reason for the following:

(i)   Dry HCl gas does not change the colour of the dry blue litmus paper.

(ii) Alcohol and glucose also contain hydrogen but do not conduct electricity.

(iii)   Concentration of H3O+ ions is affected when a solution of an acid is diluted.

Q4.Explain the action of dilute hydrochloric acid on the following with chemical equation:

(i) Magnesium ribbon

(ii) Sodium Hydroxide

(iii) Crushed egg shells.

Q5.  (a) What is the action of litmus on:

                              (i) Dry ammonia gas

                              (ii) Solution of ammonia gas in water

  (b) State the observation you would make on adding sodium hydroxide to aqueous solution of:

                              (i)  Ferrous Sulphate

                              (ii) Aluminium chloride

               Give balanced chemical equation.

Q6. A few crystals of copper sulphate are heated in dry boiling tube:

(i) What is the colour before and after heating?

(ii) What is the reason for the colour change?

(iii) Can its original colour be restored? How?

Q7. A sanitary worker uses a white chemical having strong smell of chlorine gas to disinfect the water tank.

(i) Identify the chemical compound, write its chemical formula.

(ii) Give chemical equation for its preparation.

(iii) Write its two uses other than disinfection.

Q8. “Sodium hydrogen carbonate is a basic salt. “Justify the statement. How is it converted into washing soda? Explain. 

Q9. To an aqueous solution of sodium hydroxide, a few drops of phenolphthalein were added. What do you observe?  To this solution small amount of dil. HCI was added. What do you observe now? Explain your answer.

Q10.  Answer the following.

(a) Why is sodium hydrogen carbonate an essential ingredient in ant-acids?

(b) What happens, when crystals of washing soda are left open in dry air?

(c) Why does milkman add a small amount of baking soda to fresh milk?

Q11. (a) Why curd or sour substances should not be kept in brass and copper vessels?

            (b) Aqueous solution of HI shows acidic character, whereas aqueous solution of glucose does not. Why?

            (c) What will you observe when a small amount of copper oxide is added in a beaker containing dilute Hydrochloric Acid?

5 MARK QUESTION 

Q1. Give one  example in each case:

(i)  A basic oxide which is soluble in water.

(ii)   A basic oxide which is insoluble in water.

(iii) A weak mineral acid.

(iv)   A base which is not an alkali.

(v) A hydrogen-containing compound which is not an acid.

Q2.         (i)  What is meant by pH?

                 (ii)   Two solutions A and B have pH values of 3.0 and 9.5   respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink?

(iii)   Water is a  neutral substance.   What colour will you get when you add a few drops of universal indicator to a  test tube containing distilled water?

Q3. A metal carbonate X on heating with acid gives a  gas which when passed through a  solution Y  gives the carbonate back.  On the other hand, a  gas  G that is obtained at the anode  during electrolysis of brine is passed on dry   Y,  it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G and Z.

Q4. (i) Bee-sting leaves a chemical substance that causes pain and irritation. Name the chemical substance. Identify the type of substance which may give relief on the sting area when applied on it.

        (ii) Mention the pH value below which tooth decay begins. How this fall below this value? Explain the ill effect of the acidic medium in the mouth. How can this be prevented?

         (iii) What are strong acids and weak acids? Give an example of each

Q5. (a) Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is:

(i)    neutral

(iii) strongly acidic

(ii)  strongly alkaline

(iv) weakly acidic

(v)  weakly alkaline?

Arrange the solutions in increasing order of H+ ion concentration.

(b) Name the acid and base from which the following salts have been formed.

(i) Sodium Acetate

(ii) Ammonium Chloride

Q6. (i) Dry pellets of a base ‘X’, when kept in open, absorbs moisture and turns sticky. The compound is also formed by Chloro-alkali process.  Write the chemical name and formula of X. Describe chloro­-alkali process with a balanced chemical equation. Name the type of reaction that occurs when X is treated with dilute hydrochloric acid. Write the chemical equation.

       (ii) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Q7.Give suitable reasons for the following statements:

(i) Rainwater conducts electricity but distilled water does not.

(ii) We feel burning sensation in the stomach when we overeat.

(iii) A tarnished copper vessel regains its shine when rubbed with lemon.

(iv) The crystals of washing soda change to white powder on exposure to air.

(v) An aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic.

Q8. (i) Write the chemical name and chemical formula of washing soda.

         (ii) How is it obtained from sodium chloride? Give equations of the reaction.

          (iii) Why is it called a basic salt? Give its anyone use.

 Q9.   Answer  the following:

(i) What happens when a concentrated solution of sodium chloride is electrolysed?  Write the equation of the reaction involved.

(ii)  Why is the electrolysis of a concentrated solution of sodium chloride known as Chlor- alkali process?

(iii)   Name three products of the  Chlor-alkali process. State two uses of each product.

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