1
AIIMS 2019
MCQ (Single Correct Answer)
+1
-0.33

Assertion : ZnO becomes yellow when it is heated.

Reason : The anionic sites occupied by unpaired electrons (due to F-centres).

A
If both assertion and reason are true and reason is the correct explanation of assertion.
B
If both assertion and reason are true, but reason is not the correct explanation of assertion.
C
If assertion is true, but reason is false.
D
If both assertion and reason are false.
2
AIIMS 2018
MCQ (Single Correct Answer)
+1
-0.33

Which of the following is an example of network solid?

A
$$\mathrm{SO}_2$$ (solid)
B
$$\mathrm{I}_2$$
C
Diamond
D
$$\mathrm{H}_2 \mathrm{O}$$ (ice)
3
AIIMS 2018
MCQ (Single Correct Answer)
+1
-0.33

Niobium crystallises in body centred cubic structure. If density is $$8.55 \mathrm{~g} \mathrm{~cm}^{-3}$$, then the atomic radius of niobium is (atomic mass of niobium $$=93 u$$ )

A
163 pm
B
143 pm
C
182 $$\mathop A\limits^o $$
D
152 $$\mathop A\limits^o $$
4
AIIMS 2018
MCQ (Single Correct Answer)
+1
-0.33

A solid has a structure in which W atoms are located at the corners of a cubic lattice. O atoms at the centre of edges and Na atom at centre of the cube. The formula for the compound is

A
$$\mathrm{NaWO}_2$$
B
$$\mathrm{NaWO}_3$$
C
$$\mathrm{Na}_2 \mathrm{WO}_3$$
D
$$\mathrm{NaWO}_4$$
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