1
MCQ (Single Correct Answer)

AIPMT 2012 Prelims

Which one of the alkali metals, forms only, the normal oxide, M2O on heating in air?
A
Rb
B
K
C
Li
D
Na

Explanation

When alkali metals are heated in atmosphere of oxygen the alkali metals ignite and form oxides. On combustion, Li forms Li2O, sodium gives the peroxide Na2O2 while K and Rb give super oxides (MO2).
2
MCQ (Single Correct Answer)

AIPMT 2011 Prelims

Which one of the following is present as an active ingredient in bleaching powder for bleaching action?
A
CaOCl2
B
Ca(OCl)2
C
CaO2Cl
D
CaCl2

Explanation

Active ingredient in bleaching powder for bleaching action is Ca(OCl)2, i.e., calcium hypochlorite.
3
MCQ (Single Correct Answer)

AIPMT 2011 Mains

Match List-I with List-II for the compositions of substances and select the correct answer using the code given above.

List-I
(Substances)
List-II
(Composition)
(A) Plaster of Pairs (i) CaSO4$$ \cdot $$2H2O
(B) Epsomite (ii) CaSO4$$ \cdot $$1/2 H2O
(C) Kieserite (iii) MgSO4$$ \cdot $$7H2O
(D) Gypsum (iv) MgSO4$$ \cdot $$H2O
(v) CaSO4
A
(A)-(iii),  (B)-(iv),  (C)-(i),  (D)-(ii)
B
(A)-(ii),  (B)-(iii),  (C)-(iv),  (D)-(i)
C
(A)-(i),  (B)-(ii),  (C)-(iii),  (D)-(iv)
D
(A)-(iv),  (B)-(iii),  (C)-(ii),  (D)-(i)

Explanation

(A) Plaster of paris = CaSO4.$${1 \over 2}$$H2O

(B) Epsomite = MgSO4.7H2O

(C) Kieserite = MgSO4.H2O

(D) Gypsum = CaSO4.2H2O
4
MCQ (Single Correct Answer)

AIPMT 2011 Prelims

Which of the following compounds has the lowest melting point?
A
CaCl2
B
CaBr2
C
CaI2
D
CaF2

Explanation

As the covalent character in compound increases and ionic character decreases, melting point of the compound decreases. So, CaI2 has the highest covalent character and lowest melting point.

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