Chemistry PRACTICALS CLASS XI

Q. 1.    The given impure sample is purified by dissolving it in water, then filtering and heating the solution in a Chine dish till saturation followed by cooling to get the pure substance. This technique is called as:

(a) Separation

(b) Crystallisation

(c) Fractional Crystallisation

(d) Evaporation

Q. 2. We use concentrated sulphuric acid to determine the melting point of the organic compound because:

(a) sulphuric acid is easily available in the laboratory

(b) sulphuric acid is easy to handle

(c) sulphuric acid has low boiling point

(d) it has high boiling point and is stable when heated

Q. 3.  Some of the liquid substance have very high boiling points because they have :

(a) high molecular mass and strong intermolecular forces

(b) low molecular mass and weak intermolecular forces

(c) high molecular mass and weak intermolecular forces

(d) low molecular mass and weak intermolecular forces

Q. 4. "Purity" of a substance is best determined by :

(a) melting point

(b) boiling point

(c) crystallization point

(d) freezing point

Q. 5.  On adding ammonium chloride to ammonium hydroxide solution, pH of ammonium hydroxide solution will :

(a) increase

(b) decrease

(c) remain same

(d) none of these

Q. 6. There are four different solutions in four test tubes A, B, C and D. The pH value of these solutions are 12, 5, 7 and 13 respectively. Acid is present in :

(a) test tube A and B both

(b) test tube B only

(c) test tube C and D only both

(d) test tube A and D both

Q. 7. An unknown solution A is taken in the test tube whose pH value has been found to be 12.0. Another solution B is added to the solution A drop by drop. If the pH of the solution A changes to 5 after sometime, then the solution B is :

(a) water

(b) base

(c) acid

(d) salt solution

Q. 8.    A complex is formed when HCl is added to a solution containing COCl₂. The complex is :

_]2+

(a) [Co(H₂O)_6]2–

(b) [CoCl_4]2+

(c) [CoCl₄

(d) [Co(H₂O₆Cl₂]

Q. 9.  An equilibrium is attained when we mix 10 ml of 0.1 M cobalt nitrate solution and 10 ml of 0.1 hydrochloric acid. The colour of the solution at equilibrium is pink. What shall be added to the solution to shift the equilibrium to the right direction with the change in colour from pink to blue?

(a) Water

(b) Brine solution

(c) Hydrochloric acid

(d) Nitric acid

Q. 10. The solution of the complex formed by mixing FeCl₃ with KCNs is taken into four test tubes, 1, 2, 3 &

4. Then water, ferric chloride, sodium chloride and sodium sulphate solutions are added to the test tubes respectively. The colour of the solution becomes dark in the test tube :

(a) 1 and 4

(b) 2

(c) 1 and 3

(d) 4

Q. 11. The solution which cannot be considered as a primary standard solution is :

(a) Mohr's salt solution

(b) oxalic and solution

(c) sodium hydroxide solution

(d) sodium carbonate solution

Q. 12. The strength of oxalic acid in g/L if 20 ml of M/10 sodium hydroxide is used to neutralize 10 ml of oxalic acid solution will be :

(a) 0.126 g/L

(b) 1.26 g/L

(c) 0.63 g/L

(d) 6.3 g/L

Q. 13. Following are the given steps of Acid-Base titration :

(i) filling of burette or conical flask of Acid-Base titration

(ii) rinsing of burette or pipette

(iii) titration

(a) H₃O⁺

(b) OH^–

(c) –C₂O₄

(d) Na⁺

Q. 16. The quantity of oxalic acid needed to prepare 100 ml of M/10 oxalic acid solution is : [Molecular wt. of oxalic acid is 126 u]

(a) 1.26 gm

(b) 63 gm

(c) 12.6 gm

(d) 6.3 gm

Q. 17. 20 ml of water is added to 20 ml of M/20 sodium carbonate solution in the conical flask. The molarity of the solution obtained will be :

(a) M/10

(b) M/20

(c) M/30

(d) M

Q. 18. On addition of ammonium chloride to ammonium hydroxide solution, pH of ammonium hydroxide will :

(a) increase due to decrease in OH^– ion

(b) decrease due to increase in NH⁺_n ion

(c) remain same as if forms buffer solution

(d) decrease due to decrease in OH^– ion

Q. 19. Lead is included in Ist as well as IInd group of cation analysis because :

(a) lead ion is insoluble in dil. HCl

(b) lead does not give Ist group test easily

(c) lead chloride is sparingly soluble in dil. HCl

(d) none of the above

Q. 20. Original solution is not prepared in conc. HNO₃ or H₂SO₄ because :

(a) they are strong acids

(b) they do not dissolve any salt

(c) they oxidize H₂S and form insoluble salts

(d) none of the above

Q. 21. Sodium carbonate cannot be used in place of ammonium carbonate for the identification of group V radicals. This is because :

(a) sodium ions interfere in the detection of group V radicals

(b) concentration of carbonate ions is very low

(c) sodium will react with the acid radicals

(d) magnesium will be precipitated

Q. 22. Only group IInd and IV cations get precipitated as sulphides on passing H₂S gas through the solution. But on passing H₂S gas in acidic medium cations of only group II get precipitated due to :

(a) high solubility product of group IV sulphides

(b) high solubility product of group II sulphides

(c) low solubility product of group IV sulphides

(d) low solubility product of sulphides of group II

Q. 23. When an unknown salt is treated with dilute H₂SO₄ solution, the gas liberated has the smell of rotten eggs which when passed through lead acetate solution turns black. The ion in the unknown salt is :

(a) acetate ion

(b) nitrite ion

(c) carbonate ion

(d) sulphuric ion

Q. 24. The product formed by mixing the solution of potassium ferrocyanide with ferric chloride solution is :

(a) ferro-ferricyanide

(b) ferric-ferrocyanide

(c) ferri-ferricyanide

(d) none

Q. 25. During Lassiagne's test for identification of nitrogen, sulphur and halogens in the organic compound, the formation of red coloured compound on addition of ferric chloride to Lassaigne's solution indicates the presence of :

(a) nitrogen only

(b) nitrogen and sulphur

(c) sulphur only

(d) chlorine only

Answer Key

Q.No. Answer Q.No. Answer

1. (b)    14. (a)

2. (d)    15. (a)

3. (a)    16. (a)

4. (a)    17. (d)

5. (b)    18. (c)

6. (b)    19. (c)

7. (c)    20. (c)

8. (b)    21. (d)

9. (c)    22. (a)

10. (b) 23. (d)

11. (c) 24. (a)

12. (a) 25. (b)

13. (b)