CBSE Class 12 Chemistry P Block Elements VBQs

Question. In which of the following compounds, nitrogen exhibits highest oxidation state?
(a) N₂H₄
(b) NH₃
(c) N₃H
(d) NH₂OH 
Answer. C

Question. Nitrogen forms N₂, but phosphorus does not form P₂, however, it converts P₄, reason is
(a) triple bond present between phosphorus atom
(b) pp – pp bonding is weak
(c) pp – pp bonding is strong
(d) multiple bonds form easily. 
Answer. B

Question. Which of the following oxides is most acidic?
(a) As₂O₅
(b) P₂O₅
(c) N₂O₅
(d) Sb₂O₅ 
Answer. C

Question. Which of the following has the highest dipole moment?
(a) SbH₃
(b) AsH₃
(c) NH₃
(d) PH₃
Answer. C

Question. The basic character of hydrides of the V group elements decreases in the order
(a) NH₃ > PH₃ > AsH₃ > SbH₃
(b) SbH₃ > AsH₃ > PH₃ > NH₃
(c) SbH₃ > PH₃ > AsH₃ > NH₃
(d) NH₃ > SbH₃ > PH₃ > AsH₃
Answer. A

Question. Among the following oxides, the lowest acidic is
(a) As₄O₆
(b) As₄O₁₀
(c) P₄O₆
(d) P₄O₁₀ 
Answer. A

Question. Which of the following fluorides does not exist?
(a) NF₅
(b) PF₅
(c) AsF₅
(d) SbF₅
Answer. A

Question. Which one has the lowest boiling point?
(a) NH₃
(b) PH₃
(c) AsH₃
(d) SbH₃
Answer. B

Question. Number of electrons shared in the formation of nitrogen molecule is
(a) 6
(b) 10
(c) 2
(d) 8 
Answer. A

Question. Nitrogen is relatively inactive element because
(a) its atom has a stable electronic configuration
(b) it has low atomic radius
(c) its electronegativity is fairly high
(d) dissociation energy of its molecule is fairly high.
Answer. D

Question. Pure nitrogen is prepared in the laboratory by heating a mixture of
(a) NH₄OH + NaCl
(b) NH₄NO₃ + NaCl
(c) NH₄Cl + NaOH
(d) NH₄Cl + NaNO₂. 
Answer. D

Question. Which of the following statement is not correct for nitrogen?
(a) Its electronegativity is very high.
(b) d-orbitals are available for bonding.
(c) It is a typical non-metal.
(d) Its molecular size is small. 
Answer. B

Question. Urea reacts with water to form A which will decompose to form B. B when passed through Cu²⁺ _(aq), deep blue colour solution C is formed. What is the formula of C from the following?
(a) CuSO₄
(b) [Cu(NH₃)₄]²⁺
(c) Cu(OH)₂
(d) CuCO₃·Cu(OH)₂
Answer. B

Question. Aqueous solution of ammonia consists of
(a) H⁺
(b) OH^–
(c) NH₄⁺
(d) NH₄⁺ and OH^–.
Answer. D

Question. Which of the following oxides of nitrogen is paramagnetic?
(a) NO₂
(b) N₂O₃
(c) N₂O
(d) N₂O₅
Answer. A

Question. Which of the following is a nitric acid anhydride?
(a) NO
(b) NO₂
(c) N₂O₅
(d) N₂O₃
Answer. C

Question. When copper is heated with conc. HNO₃ it produces
(a) Cu(NO₃)₂, NO and NO₂
(b) Cu(NO₃)₂ and N₂O
(c) Cu(NO₃)₂ and NO₂
(d) Cu(NO₃)₂ and NO 
Answer. C

Question. Zn gives H₂ gas with H₂SO₄ and HCl but not with HNO₃ because
(a) Zn act as oxidising agent when react with HNO₃
(b) HNO₃ is weaker acid than H₂SO₄ and HCl
(c) in electrochemical series Zn is above hydrogen
(d) NO₃^– is reduced in preference to hydronium ion. 
Answer. D

Question. Sugarcane on reaction with nitric acid gives
(a) CO₂ and SO₂
(b) (COOH)₂
(c) 2HCOOH(two moles)
(d) no reaction. 
Answer. B

Question. Which of the following phosphorus is the most reactive?
(a) Scarlet phosphorus
(b) White phosphorus
(c) Red phosphorus
(d) Violet phosphorus
Answer. B

Question. Each of the following is true for white and red phosphorus except that they
(a) are both soluble in CS₂
(b) can be oxidised by heating in air
(c) consist of the same kind of atoms
(d) can be converted into one another. 
Answer. A

Question. A compound ‘X’ upon reaction with H₂O produces a colourless gas ‘Y’ with rotten fish smell. Gas ‘Y’ is absorbed in a solution of CuSO₄ to give Cu₃P₂ as one of the products. Predict the compound ‘X’.
(a) Ca₃P₂
(b) NH₄Cl
(c) As₂O₃
(d) Ca₃(PO₄)₂
Answer. A

Question. PH₄I + NaOH forms
(a) PH₃
(b) NH₃
(c) P₄O₆
(d) P₄O₁₀
Answer. A

Question. Identify the incorrect statement related to PCl₅ from the following :
(a) PCl₅ molecule is non-reactive.
(b) Three equatorial P – Cl bonds make an angle of 120° with each other.
(c) Two axial P – Cl bonds make an angle of 180° with each other.
(d) Axial P – Cl bonds are longer than equatorial P – Cl bonds.
Answer. A

Question. PCl₃ reacts with water to form
(a) PH₃
(b) H₃PO₃, HCl
(c) POCl₃
(d) H₃PO₄ 
Answer. B

Question. Which of the following oxoacids of phosphorus has strongest reducing property?
(a) H₄P₂O₇
(b) H₃PO₃
(c) H₃PO₂
(d) H₃PO₄
Answer. C

Question. Which is the correct statement for the given acids?
(a) Phosphinic acid is a monoprotic acid while phosphonic acid is a diprotic acid.
(b) Phosphinic acid is a diprotic acid while phosphonic acid is a monoprotic acid.
(c) Both are diprotic acids.
(d) Both are triprotic acids. 
Answer. A

Question. Strong reducing behaviour of H₃PO₂ is due to
(a) high electron gain enthalpy of phosphorus
(b) high oxidation state of phosphorus
(c) presence of two —OH groups and one P—H bond
(d) presence of one —OH group and two P—H bonds.
Answer. D

Question. Which of the following statements is not valid for oxoacids of phosphorus?
(a) Orthophosphoric acid is used in the manufacture of triple superphosphate.
(b) Hypophosphorous acid is a diprotic acid.
(c) All oxoacids contain tetrahedral four coordinated phosphorus.
(d) All oxoacids contain atleast one P O unit and one P—OH group. 
Answer. B

Question. Oxidation states of P in H₄P₂O₅, H₄P₂O₆, H₄P₂O₇ are respectively
(a) +3, +5, +4
(b) +5, +3, +4
(c) +5, +4, +3
(d) +3, +4, +5 
Answer. D

Question. How many bridging oxygen atoms are present in P₄O₁₀?
(a) 6
(b) 4
(c) 2
(d) 5
Answer. A

Question. H₃PO₂ is the molecular formula of an acid of phosphorus. Its name and basicity respectively are
(a) phosphorous acid and two
(b) hypophosphorous acid and two
(c) hypophosphorous acid and one
(d) hypophosphoric acid and two. 
Answer. C

Question. Which one of the following substance is used in the laboratory for fast drying of neutral gases?
(a) Phosphorus pentoxide
(b) Active charcoal
(c) Anhydrous calcium chloride
(d) Na₃PO₄
Answer. A

Question. P₂O₅ is heated with water to give
(a) hypophosphorous acid
(b) phosphorous acid
(c) hypophosphoric acid
(d) orthophosphoric acid. 
Answer. D

Question. Basicity of orthophosphoric acid is
(a) 2
(b) 3
(c) 4
(d) 5 
Answer. B

Question. When orthophosphoric acid is heated to 600°C, the product formed is
(a) PH₃
(b) P₂O₅
(c) H₃PO₃
(d) HPO₃ 
Answer. D

Question. Which is the correct thermal stability order for H₂E (E = O, S, Se, Te and Po) ?
(a) H₂Se < H₂Te < H₂Po < H₂O < H₂S
(b) H₂S < H₂O < H₂Se < H₂Te < H₂Po
(c) H₂O < H₂S < H₂Se < H₂Te < H₂Po
(d) H₂Po < H₂Te < H₂Se < H₂S < H₂O
Answer. D

Question. Acidity of diprotic acids in aqueous solutions increases in the order
(a) H₂S < H₂Se < H₂Te
(b) H₂Se < H₂S < H₂Te
(c) H₂Te < H₂S < H₂Se
(d) H₂Se < H₂Te < H₂S
Answer. A

Question. Ammonium nitrate is used as a high nitrogen fertilizer in agriculture. It is also used in instant cold packs. It is mixed with fuel oil and used as explosive. Due to its various uses its production cannot be banned.
(a) What are cold packs?
(b) What steps Indian government has taken to avoid the misuse of ammonium nitrate by terrorists?
(c) What values are needed by an individual while handling such chemicals?
Answer:

(a) They contain ammonium nitrate and water. Endothermic reaction gives cooling effect and relieves pain
(b) Only authorized dealers can sell ammonium nitrate
(c) Proper knowledge about the properties of the chemicals, misuse should be avoided, Chemical should be used only for the welfare of mankind

Question. In recent years, the excessive uses of some aerosol propellants and refrigerants have depleted the ozone layer.
(a) Name two chemicals which deplete the ozone layer in the stratosphere.
(b) What is the importance of ozone in the stratosphere?
(c) Suggest some measures for minimizing global warming.

Answer:
(a) NO, CFC’S
(b) Prevents entry of harmful ultraviolet radiations in earth’s atmosphere.
(c) Minimising the usage of CFC’S, fossil fuels etc.

Question. Student accidently spills concentrated H2SO4 on his hand. Before the teacher gets to know, his friend washed his hands with water and also with soap but the burning sensation on hand was still going on. The friend then rubs solid sodium bicarbonate on his hand and then washed with water; finally the burning sensation is relieved.

(i) Mention the values shown by student’s friend.
(ii) Can you recommend any other substance available in the laboratory which can be used instead of sodium bicarbonate?
Answer:

(i) Concern and care for others and application of scientific knowledge
(ii) Slaked lime  

Question. India's top court ruled that authorities must regulate the sale of acid used in a spate of attacks on women. An acid called "Tezaab", which is designed to clean rusted tools but is often used in the attacks, can currently be bought across the counter. But the judges said the buyer of such acids should in future have to provide a photo identity card to any retailer when they make a purchase. The retailers must register the name and address of the buyer.

(a) Why are acid burns harmful?
(b) What are the values associated with the above discussion?
(c) What are responsibilities of the citizens in this regard?

Answer:

(a) Stringent measures to prevent misuse of acid
(b) They are highly corrosive.
(c) Help in preventing such incidences and helping victims , bringing to the notice of authorities such incidences 

Question. In a paper industry hydrogen peroxide is used bleaching agent. Satish asked his friend about using chlorine as bleaching agent. His friend told that using hydrogen peroxide was better.
(a) What is the disadvantage of using chlorine as bleaching agent?
(b) Why is use of hydrogen peroxide better?

Answer:
(a) HCl is the bye product in case Cl is used as a bleaching agent
(b) Water is the bye product. 

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