The compound A on heating gives a colourless gas and a residue that is dissolved in water to obtain B. Excess of CO2 is bubbled through aqueous solution of B, C is formed which is recovered in the solid form. Solid C on gentle heating gives back A. The compound is
A
CaCO3
B
Na2CO3
C
K2CO3
D
CaSO4$$ \cdot $$2H2O
Explanation
A $$\buildrel \Delta \over
\longrightarrow $$
colourless gas + residue
Residue + H2O $$ \to $$ B $$\buildrel {excess\,\,C{O_2}} \over
\longrightarrow $$ C $$\buildrel \Delta \over
\longrightarrow $$ A
This is possible only when ‘A’ is CaCO3. The
reactions are as follow :
2
AIPMT 2010 Prelims
MCQ (Single Correct Answer)
Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?
A
CaSO4
B
BeSO4
C
BaSO4
D
SrSO4
Explanation
The hydration enthalpy of BeSO4
is higher
than its lattice energy. Within group 2, the hydration
energy decreases down the group while lattice
energy is almost the same.
3
AIPMT 2010 Prelims
MCQ (Single Correct Answer)
Property of the alkaline earth metals that increases with their atomic number
A
solubility of their hydroxides in water
B
solubility of their sulphates in water
C
ionization energy
D
electronegativity
Explanation
On moving down the group, basic nature of
these hydroxides increases due to low ionization
enthalpies because M-O bond in MOH is weak and
thus break to give OH– ions in the solution.
4
AIPMT 2009
MCQ (Single Correct Answer)
Which of the following oxides is not expected to react with sodium hydroxide?
A
CaO
B
SiO2
C
BeO
D
B2O3
Explanation
NaOH is a strong alkali. It combines with
acidic and amphoteric oxides to form salts. Since
CaO is a basic oxide hence does not reacts with
NaOH.
Questions Asked from s-Block Elements
On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
