p-Block Elements · JEE Main previous year questions

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2021 16 questions

Q802021 · 1 Sept 2021 · Shift 2
The oxide without nitrogen-nitrogen bond is :
1. A. $N_{2} O$
2. B. $N_{2} O_{4}$
3. C. $N_{2} O_{3}$
4. D. $N_{2} O_{5}$
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Answer: D
Q722021 · 26 Aug 2021 · Shift 2
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Photochemical smog causes cracking of rubber. Reason (R) : Presence of ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyl nitrate in photochemical smog makes it oxidizing. Choose the most appropriate answer from the options given below :
1. A.Both (A) and (R) are true but (R) is not the true explanation of (A)
2. B.(A) is false but (R) is true.
3. C.(A) is true but (R) is false.
4. D.Both (A) and (R) are true and (R) is the true explanation of (A)
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Answer: D
Q812021 · 26 Aug 2021 · Shift 2· Numerical answer
In the sulphur estimation, 0.471 g of an organic compound gave 1.44 g of barium sulphate. The percentage of sulphur in the compound is ____________%. (Nearest integer) (Atomic Mass of Ba = 137 u)
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Answer: 42
Q692021 · 27 Jul 2021 · Shift 2
Match List - I with List - II : | | List - I (compound) | | List - II (effect/affected species) | |---|---|---|---| | (a) | Carbon monoxide | (i) | Carcinogenic | | (b) | Sulphur dioxide | (ii) | Metabolized by pyrus plants | | (c) | Polychlorinated biphenyls | (iii) | haemoglobin | | (d) | Oxides of Nitrogen | (iv) | Stiffness of flower buds | Choose the correct answer from the options given below :
1. A.(a) - (iii), (b) - (iv), (c) - (i), (d) - (ii)
2. B.(a) - (iv), (b) - (i), (c) - (iii), (d) - (ii)
3. C.(a) - (i), (b) - (ii), (c) - (iii), (d) - (iv)
4. D.(a) - (iii), (b) - (iv), (c) - (ii), (d) - (i)
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Answer: A
Q652021 · 25 Jul 2021 · Shift 1
[structure: phenol] $⟶$ [structure: p-bromophenol] (Major Product) The given reaction can occur in the presence of : (a) Bromine water (b) $B r_{2}$ in $C S_{2}$ , 273 K (c) $B r_{2} /FeB r_{3}$ (d) $B r_{2}$ in $CHC l_{3}$ , 273 K Choose the correct answer from the options given below :
1. A.(b) and (d) only
2. B.(a) and (c) only
3. C.(b), (c) and (d) only
4. D.(a), (b) and (d) only
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Answer: C
Q792021 · 25 Jul 2021 · Shift 2
Given below are two statements : Statement I : Chlorofluoro breakdown by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone. Statement II : Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases, which add to the atmosphere. For the above statements choose the correct answer from the options given below :
1. A.Statement I is incorrect but Statement II is true
2. B.Both Statement I and II are false
3. C.Statement I is correct but Statement II is false
4. D.Both Statement I and II are correct
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Answer: B
Q782021 · 22 Jul 2021 · Shift 2
Given below are the statements about diborane (a) Diborane is prepared by the oxidation of $NaB H_{4}$ with $I_{2}$ (b) Each boron atom is in $s p^{2}$ hybridized state (c) Diborane has one bridged 3 centre-2-electron bond (d) Diborane is a planar molecule The option with correct statements is :
1. A.(c) and (d) only
2. B.(a) only
3. C.(c) only
4. D.(a) and (b) only
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Answer: B
Q772021 · 20 Jul 2021 · Shift 1
Chemical nature of the nitrogen oxide compound obtained from a reaction of concentrated nitric acid and $P_{4} O_{10}$ (in $4 : 1$ ratio) is :
1. A.acidic
2. B.basic
3. C.amphoteric
4. D.neutral
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Answer: A
Q862021 · 20 Jul 2021 · Shift 1· Numerical answer
The number of nitrogen atoms in a semicarbazone molecule of acetone is ______________.
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Answer: 3
Q782021 · 18 Mar 2021 · Shift 1
The number of ionisable hydrogens present in the product obtained from a reaction of phosphorus trichloride and phosphonic acid is :
1. A.3
2. B.0
3. C.2
4. D.1
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Answer: C
Q802021 · 18 Mar 2021 · Shift 1
The chemical that is added to reduce the melting point of the reaction mixture during the extraction of aluminium is :
1. A.Cryolite
2. B.Bauxite
3. C.Calamine
4. D.Kaolite
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Answer: A
Q762021 · 16 Mar 2021 · Shift 1
Match List - I with List - II : $(a) (b) (c) (d) List - I Industrial process Haber’s process Ostwald’s process Contact process Hal-Heroult process (i) (ii) (iii) (iv) List - II Application HN O_{3} synthesis Aluminium extraction N H_{3} synthesis H_{2} S O_{4} synthesis$ Choose the correct answer from the options given below :
1. A.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
2. B.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
3. C.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
4. D.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
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Answer: B
Q802021 · 16 Mar 2021 · Shift 1
The process that involves the removal of sulphur from the ores is :
1. A.Roasting
2. B.Smelting
3. C.Leaching
4. D.Refining
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Answer: A
Q772021 · 26 Feb 2021 · Shift 1
The presence of ozone in troposphere :
1. A.protects us from greenhouse effect
2. B.protects us from the UV radiation
3. C.protects us from the X-ray radiation
4. D.generates photochemical smog
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Answer: D
Q882021 · 26 Feb 2021 · Shift 1· Numerical answer
3.12 g of oxygen is adsorbed on 1.2 g of platinum metal. The volume of oxygen adsorbed per gram of the adsorbent at 1 atm and 300 K in L is _________. $[R = 0.0821 L atm K^{- 1} mo l^{- 1}]$
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Answer: 2
Q832021 · 26 Feb 2021 · Shift 2· Numerical answer
In mildly alkaline medium, thiosulphate ion is oxidized by $M n O_{4}^{-}$ to "A". The oxidation state of sulphur in "A" is _________.
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Answer: 6