ACIDS, BASES AND SALTS – 5 Mark Questions

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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