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p-Block Elements (Group 15–18) · Question 60

AIPMT 2002MCQEasy📈 Topic in 50% papers+4−1
1

Zn gives H2 gas with H2SO4 and HCl but not with HNO3 because

  1. Zn acts as oxidising agent when it reacts with HNO3
  2. HNO3 is weaker acid than H2SO4 and HCl
  3. In electrochemical series Zn is above hydrogen
  4. NO3- is reduced in preference to hydronium ion.

Answer

(4) NO3- is reduced in preference to hydronium ion.

Solution

With dilute HCl or H2SO4, the only species Zn can reduce is H3O+:

Zn + 2H3O+ Zn2+ + H2 + 2H2O

In HNO3, the nitrate ion is a stronger oxidising agent than H3O+, so NO3- is reduced (to NO2, NO, N2O or NH4+) instead of H+, e.g.

4Zn + 10HNO3(dil.) 4Zn(NO3)2 + 5H2O + N2O

No H2 is evolved because NO3- is reduced in preference to hydronium ion.

(Zn is a reducing agent, and HNO3 is a strong acid, so (1) and (2) are wrong; (3) explains H2 with HCl but not its absence with HNO3.)

Answer: (4)

AIPMT 2002

Keep practising — p-Block Elements (Group 15–18)

2

Nitrogen forms N2, but phosphorus does not form P2, however, it exists as P4, reason is

  1. triple bond present between phosphorus atoms
  2. p - p bonding is weak
  3. p - p bonding is strong
  4. multiple bonds form easily.
AIPMT 2001
3

Which statement is wrong ?

  1. Bond energy of F2 > Cl2
  2. Electronegativity of F > Cl
  3. F is more oxidising than Cl
  4. Electron affinity of Cl > F
AIPMT 2000
4

Which compound has planar structure?

  1. XeF4
  2. XeOF2
  3. XeO2F2
  4. XeO4
AIPMT 2000

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