CBSE Class 12 Chemistry Representative Elements Worksheet

Question. Which of the following statement is correct regarding alkali metals?
a. Cation is less stable than the atom
b. Cation is smaller than the atom
c. Size of cation and atom is the same
d. Cation is greater in size than the atom
Answer : B

Question. With cold and dilute sodium hydroxide fluorine reacts to give
a. NaFand OF₂
b. NaF + O₃
c. O₂ and O₃
d. NaF +O₂
Answer : A

Question. When PbO₂ reacts with conc. HNOO₃ the gas evolved is
a. NO₂
b. O₂
c. N₂
d. N₂O
Answer : B

Question. In certain matters lithium differs from other alkali metals, the main reason for this is:
a. Small size of Li atom and Li+ ion
b. Extremely high electropositivity of Li
c. Greater hardness of Li
d. Hydration of Li+ ion
Answer : A

Question. Which of the following metal has stable carbonates?
a. Na
b. Mg
c. Al
d. Si
Answer : A

Question. The right order of the solubility of sulphates of alkaline earth metals in water is:
a. Be > Ca > Mg > Ba > Sr
b. Mg > Be > Ba > Ca > Sr
c. Be >Mg > Ca > Sr > Ba
d. Mg > Ca > Ba > Be > Sr
Answer : C

Question. Setting of cement is an:
a. Exothermic reaction
b. Endothermic reaction
c. Neither exothermic nor endothermic
d. None of these
Answer : A

Question. Potassium is kept in:
a. Alcohol
b. Water
c. Kerosene
d. Liquid ammonia
Answer : C

Question. Amongst LiCl, RbCl, BeCl₂ and MgCl₂ the compounds with the greatest and least ionic character respectively are
a. LiCl and RbCl
b. MgCl₂ and BeCl₂
c. RbCl and BeCl₂
d. RbCl and MgCl₂
Answer : C

Question. Causticization process is used for the preparation of:
a. Caustic soda
b. Caustic potash
c. Baryta
d. Slaked lime
Answer : A

Question. Setting of plaster of paris is
a. Oxidation with atmospheric oxygen
b. Combination with atmospheric CO₂
c. Dehydration
d. Hydration to yield another hydrate
Answer : D

Question. Which of the following alkaline-earth metal hydroxides is the strongest base?
a. Be(OH)₂
b. Mg(OH)₂
c. Ca(OH)₂
d. Ba(OH)₂
Answer : D

Question. In the electrolytic method of obtaining aluminium from purified bauxite, cryolite is added to the charge in order to:
a. Minimize the heat loss due to radiation
b. Protect aluminium produced from oxygen
c. Dissolve bauxite and render it conductor of electricity
d. Lower the melting point of bauxite
Answer : 

Question. Sparingly soluble salt is:
a. KCl
b. NaCl
c. NH₄Cl
d. BaSO₄
Answer : 

Question. In the purification of bauxite by Hall's process
a. Bauxite ore is heated with NaOH solution at 50°C
b. Bauxite ore is fused with Na₂CO₃
c. Bauxite ore is fused with coke and heated at o 1800 C in a current of nitrogen
d. Bauxite ore is heated with 3
Answer : C

Question. Among K, Ca, Fe, and Zn , the element which can form more than one binary compound with chlorine is:
a. K
b. Ca
c. Fe
d. Zn
Answer : C

Question. Photoelectric effect is maximum in:
a. Cs
b. Na
c. K
d. Li
Answer : A

Question. Plaster of paris is used
a. In surgery and dentistry
b. As a white wash
c. As a constituent of tooth paste
d. For the preparation of RCC
Answer : A

Question. Which one of the following statements about the zeolites is false
a. Zeolites are aluminosilicates having three dimensional network
b. Some of the SiO⁻⁴₄ units are replaced by AlO⁻⁵₄ and  AlO₆⁹⁻ ions in zeolites
c. They are used as cation exchangers
d. They have open structure which enables them to take up small
Answer : B

Question. V-A group precipitate was dissolved in HNO₃ and treated with excess of NH₄ OH . It gives a white ppt. because of
a. Cu(OH)₂
b. Cd(OH)₂
c. Bi(OH)₃
d. Hg(OH)₂
Answer : C

Question. Bleaching action of SO₂ is due to its
a. Oxidising property
b. Acidic property
c. Basic property
d. Reducing property
Answer : D

Question. Noble gases are absorbed on
a. Anhydrous CaCl₂
b. Charcoal
c. Conc. H₂SO₄
d. Coconut
Answer : B

Question. In Hall’s process, the main reagent is mixed with
a. NaF
b. Na₃ AlF₆
c. AlF₃
d. None of these
Answer : B

Question. Which alkali metal carbonate decomposes on heating to liberate CO₂ gas
a. Li₂CO₃
b. CaCO₃
c. Na₂CO₃
d. Al₂CO₃
Answer : A

Question. Soldiers of Napolean army while at Alps during freezing winter suffered a serious problem as regards to the tin buttons of their uniforms. White metallic tin buttons got converted to grey powder. This transformation is related to
a. A change in the partial pressure of oxygen in the air
b. A change in the crystalline structure of tin
c. An interaction with nitrogen of the air at very low to temperatures
d. An interaction with water vapour contained in the humid air
Answer : B

Question. Lapis lazuli is:
a. Ferrous sulphate
b. Copper sulphate
c. Sodium alumino silicate
d. Zinc sulphate
Answer : C

Question. HNO₂ acts as
a. Oxidising agent
b. Reducing agent
c. Both a and b
d. Its solution is stable
Answer : C

Question. Which has the lowest boiling point?
a. NH₃
b. PH₃
c. AsH₃
d. SbH₃
Answer : D

Question. When tin is treated with concentrated nitric acid
a. It is converted into stannous nitrate
b. It is converted into stannic nitrate
c. It is converted into metastannic acid
d. It becomes passive
Answer : C

Question. In the reaction B₂O₂ + C + Cl₂ → A + CO. The A is
a. BCl₃
b. BCl₂
c. B₂ Cl₂
d. CCl₂
Answer : A

Question. Which of the following is only acidic in nature:
a. Be(OH)₂
b. Mg(OH)₂
c. B(OH)₃
d. Al(OH)₃
Answer : C

Question. Which of the following attacks glass
a. HCl
b. HF
c. HI
d. HBr
Answer : B

Question. In Birkeland-Eyde process, the raw material used is
a. Air
b. NH₃
c. NO₂
d. HNO₃
Answer : A

Question. Which compound acts as an oxidising as well as reducing agent
a. SO₂
b. MnO₂
c. Al₂O₃
d. CrO₃
Answer : A

Question. Phosphine is prepared by the reaction of
a. P and H₂SO₄
b. P and NaOH
c. P and H₂S
d. P and HNO₃
Answer : B

Question. Which nitrogen trihalides is least basic?
a. NF₃
b. NCl₃
c. NBr₃
d. NI₃
Answer : A

Question. Which of the following oxy acids of phosphorus is a reducing agent and monobasic
a. H₃PO₂
b. H₃PO₃
c. H₃ PO₄
d. H₄P₂O₆
Answer : A

Question. Bond angle is minimum for
a. H₂O
b. H₂S
c. H₂Se
d. H₂Te
Answer : D

Question. Which of the following is used in the preparation of chlorine?
a. Only MnO₂
b. Only KMnO₄
c. Both MnO₂ and KMnO₄
d. Either MnO₂ or KMnO₄
Answer : C

Question. Which of the following is formed by the action of water on sodium peroxide?
a. H₂
b. N₂
c. O₂
d. CO₂
Answer : C

Question. Based on lattice energy and other considerations which one of the following alkali metal chlorides is expected to have the highest melting point:
a. LiCl
b. NaCl
c. KCl
d. RbCl
Answer : B

Question. Slow actAing nitrogenous fertilizer among the following is
a. NH₂ CONH₂
b. NH₄NO₃
c. CaNCN
d. KNO₃
Answer : A

Question. The most efficient agent for the absorption of SO₃ is
a. 80% H₂SO₄
b. 98% H₂SO₄
c. 50% H₂SO₄
d. 20% H₂S₂O₇
Answer : B

Question. The solubility of iodine in water increases in the presence of
a. Alcohol
b. Chloroform
c. Sodium hydroxide
d. Potassium iodide
Answer : D

Question. Which has the highest molar heat of vaporisation
a. HF
b. HCl
c. HBr
d. HI
Answer : D

Question. Which one of the following statements regarding helium is incorrect?
a. It is used to produce and sustain powerful superconducting magnets
b. It is used as a cryogenic agent for carrying out experiments at low temperatures
c. It is used to fill gas balloons instead of hydrogen because it is lighter and non-inflammable
d. It is used in gas-cooled nuclear reactors
Answer : C

Question. The inert gases are
a. Polyatomic
b. Triatomic
c. Diatomic
d. Monoatomic
Answer : D

Question. Which of the following inert gas liquifies easily?
a. Kr
b. He
c. Ne
d. Ar
Answer : A

Question. Deep sea divers used to respirate is a mixture of
a. Oxygen and argon
b. Oxygen and helium
c. Oxygen and nitrogen
d. Oxygen and hydrogen
Answer : B

Question. Which of the following is planar?
a. XeF₂
b. XeO₂F
c. XeO₂F₂
d. XeF₄
Answer : D

Elements.

1. In contrast to nitrogen, phosphorous shows distinct tendency for catenation. Why?

2. N₂ is a gas while P₄ is a solid. Justify.

3. Give reason why PH3 is a weaker base than NH₃.

4. On being slowly passed through water PH3 forms bubbles while NH3 dissolves. Why is it so?

5. The H-M-H bond angle in hydrides of gp 15th decreases down the group. The thermal stability of hydrides follows the same patter. Justify.

6. How does PCl₅ exist in gaseous, liquid and solid state?

7. PCl₅ fumes in air, why?

8. Both NCl₅ and BiCl₅ do not exist. Give reason.

9. Hypophosphorous and is monoprotic. Justify giving structure.

10. Give reason why phosphoric acid is diprotic while orthophosphoric acid is triprotic.

11. Metals like Cr and Al do not dissolve in concentrated nitric acid. Give reason.

12. What is the composition of complex formed at the junction of two solutions during ring test of NO 3

13. What is the gas present in smoke screens?

14. PCl₅ is used as a chlorinating agent. Why?

15. Which elements are called “Chalcogens”? Why are they so called?

16. Name two toxic elements of gp 16.

17. Draw the cyclo – S6 allotrope of sulphur.

18. How does S occur in vapour phase at around 1000K?

19. SO₂ is reducing while TeO₂ is an oxidizing agent?

20. Give examples of neutral oxides.

21. Give equations to support amphoteric nature of Al₂O₃.

22. Ozone is the thermodynamically less stable than oxygen. Justify on basis of Gibb’s free energy change.

23. How is O₃ gas estimated quantitatively?

24. SF6 doesn’t undergo hydrolysis. Justify.

25. Boiling points of gp16 element hydrides follow the order:-
H₂ O >>> H₂ S < H₂ Se < H₂ Te Explain

26. Enthalpy of dissociation of F₂ is smaller than that of Cl₂.Justify.

27. While preparing H₂SO₄ solution from concn H₂SO₄, what precaution must be taken and why?

28. pKa of HF (3.2) is higher than that of HCl (- 7.0) Explain.

29. Name the element used in flouroscent bulbs for advertisements / display purposes.

30. Why is NO₂ coloured?

31. Despite lower Deg H^h F₂ is a stronger oxidizing agent than Cl₂. Why?

32. An inorganic lewis acid (x) shows following reactions:-
(a) It fumes in moist air.
(b) The intensity of fumes is increased if a rod dipped in NH₄OH is brought near to it.
(c) An acidic solution of X on addition of NH₄Cl / NH4OH gives ppt which dissolves in NH₄OH, no ppt with H₂S. Identify X.