Online Test — The p-Block Elements
20 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 20
The valence-shell electronic configuration of Group 15 elements is:
ns2np2
ns2np3
ns2np4
ns2np5
Explanation: Group 15 has the half-filled configuration ns2np3.
Question 2 of 20
The catalyst used in the Haber process is:
V2O5
Pt/Rh
finely divided Fe
Ni
Explanation: The Haber synthesis of NH3 uses finely divided iron with a molybdenum promoter.
Question 3 of 20
Nitric acid is manufactured industrially by the:
Contact process
Ostwald process
Haber process
Solvay process
Explanation: The Ostwald process oxidises NH3 to NO to NO2, then to HNO3.
Question 4 of 20
The basicity of H3PO3 is:
1
2
3
4
Explanation: H3PO3 has two ionisable P–OH groups, so it is dibasic.
Question 5 of 20
Which allotrope of phosphorus is the most reactive and is stored under water?
red
black
white
violet
Explanation: White phosphorus (P4) is highly reactive and stored under water to prevent ignition.
Question 6 of 20
In the solid state, PCl5 exists as:
covalent trigonal bipyramidal molecules
[PCl4]+[PCl6]- ions
PCl3 and Cl2
a dimer P2Cl10
Explanation: Solid PCl5 is ionic, made of tetrahedral [PCl4]+ and octahedral [PCl6]-.
Question 7 of 20
The catalyst in the Contact process for converting SO2 to SO3 is:
Fe
Pt only
V2O5
Al2O3
Explanation: V2O5 catalyses 2SO2 + O2 ⇌ 2SO3.
Question 8 of 20
Ozone is prepared by passing silent electric discharge through:
moist air
dry oxygen
carbon dioxide
nitrogen
Explanation: 3O2 → 2O3 occurs in a silent electric discharge through dry O2.
Question 9 of 20
The correct order of acidic strength of the oxoacids of chlorine is:
HOCl > HClO2 > HClO3 > HClO4
HClO4 > HClO3 > HClO2 > HOCl
HClO3 > HClO4 > HOCl > HClO2
all are equal
Explanation: Acid strength rises with the oxidation state of Cl: HClO4 > HClO3 > HClO2 > HOCl.
Question 10 of 20
Which halogen has the lowest bond dissociation enthalpy?
F2
Cl2
Br2
I2
Explanation: Bond enthalpy order is Cl2 > Br2 > F2 > I2; the large I2 is weakest.
Question 11 of 20
The shape of the ClF3 molecule is:
trigonal planar
pyramidal
T-shaped
tetrahedral
Explanation: ClF3 has 3 bond pairs and 2 lone pairs (sp3d), giving a T-shape.
Question 12 of 20
Hydrogen chloride is prepared in the laboratory by heating NaCl with concentrated:
HNO3
H2SO4
NaOH
H3PO4
Explanation: NaCl + H2SO4 → NaHSO4 + HCl on heating.
Question 13 of 20
Which of the following noble gases is most abundant in the atmosphere?
He
Ne
Ar
Kr
Explanation: Argon makes up about 0.9% of air, the highest of the noble gases.
Question 14 of 20
The shape of XeF4 according to VSEPR theory is:
tetrahedral
square planar
see-saw
octahedral
Explanation: XeF4 has 4 bond pairs and 2 lone pairs (sp3d2), giving a square planar shape.
Question 15 of 20
The hybridisation of xenon in XeF2 is:
sp
sp3
sp3d
sp3d2
Explanation: XeF2 has 2 bond pairs and 3 lone pairs, so Xe is sp3d hybridised (linear).
Question 16 of 20
Complete hydrolysis of XeF6 gives:
XeO3
XeO4
XeOF4
XeF4
Explanation: XeF6 + 3H2O → XeO3 + 6HF.
Question 17 of 20
Assertion: NH3 is more basic than PH3. Reason: nitrogen is smaller and more electronegative, giving a more available lone pair. Choose the correct option.
Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation
A is true, R is false
A is false, R is true
Explanation: The smaller, more electronegative N concentrates lone-pair density, so NH3 is the stronger base — R correctly explains A.
Question 18 of 20
Which noble gas is obtained mainly from natural gas rather than liquid air?
Ne
Ar
He
Kr
Explanation: Helium accumulates in natural gas from radioactive α-decay and is recovered from it.
Question 19 of 20
Concentrated nitric acid renders which metal passive?
copper
zinc
iron
magnesium
Explanation: Concentrated HNO3 forms a protective oxide layer that passivates iron (also Cr and Al).
Question 20 of 20
Which species correctly matches its shape?
XeF2 — bent
BrF5 — square pyramidal
PCl5 (gas) — square planar
SO2 — linear
Explanation: BrF5 has 5 bond pairs and 1 lone pair (sp3d2), giving a square pyramidal shape.