(1) Answer must be written either in English or the medium of instruction of the candidate in high school.
(2) There will be no negative marking
(3) Use of calculators or graph papers is not permitted
(4) Answer all the questions.
1. To the mixture of aqueous solution of a Nitrate salt and Ferrous sulphate, con.H2SO4 is slowly added through the slanted walls of the test tube. A brown ring is formed little above (nearly middle) the bottom of the test tube. [9 Marks]
a) What is the significance of this test?
b) Which acts as reductant?
c) What is the change of oxidation state of oxidant?
d) What is the chemical composition of the Brown’s ring?
e) Why con.H2SO4 is added only through the slanted walls of the test tube?
f) Write the related chemical equations for above chemical changes.
2. It is observed that a solid mixture of chloride salt and potassium dichromate is heated with con.H2SO4 red vapours are formed. When these vapours are passed into aqueous caustic soda solution yellow solution is formed. This on further treatment with lead acetate solution, a yellow precipitate is formed. [7½ Marks]
a) What is significance of the sequence of reactions?
b) What is the name and formula of the red vapours?
c) Why red vapours are changed to yellow solution? And write its formula
d) What is the yellow precipitate formed in the last step and its formula?
e) Write the related chemical equations for above chemical changes.
3. a) What is carbohydrate? [8 Marks]
b) How atmospheric CO2 is transformed into carbohydrate in green plants?
Indicate through chemical equation?
c) What is Tollen’s test?
d) What is significance of Tollen’s test in carbohydrates?
e) What chemical changes takes place during the test?
f) Glucose gives Tollen’s test but not sucrose why?
g) What is oxidant in this reaction?
h) What is the formula of the red precipitate formed in Benedict’s test conducted
4. 0.1 moles/lit of a weak acid solution contains 0.001 moles/lit of the conjugate base (B-). [7½ Marks]
a) What is the dissociation constant (Ka) of the acid?
b) Calculate the pH of 0.1M solution of weak acid (AH)?
c) This acid is neutralized by adding required quantity of aqueous NaOH
solution. What is the approximate the range of pH of solution?
d) To the original solution HCl is added. What happens to the ratio of conjugate
base to the acid and how Ka of the acid is affected?
e) To the above original solution sodium salt of same weak acid is added. What
happens to the pH of the solution?
5. In each sub question below a statement S and an explanation E is given. Choose the correct answer from the codes A,B,C,D,E given below for each question.
(A) S is correct but E is incorrect
(B) S is incorrect but E is correct
(C) Both S and E are correct and E is correct explanation of S
(D) Both S and E are correct but E is not correct explanation of S
(E) Both S and E are incorrect
6. Match each of the molecules in Column I with its property / properties given in corresponding Column II. [10 Marks]