Which one of the following will dissolve in water most readily?

• I₂

• BaCO₃

• KF

• PbI₂

In silica (SiO₂), each silicon atom is bonded to

• two oxygen atoms

• four oxygen atoms

• one silicon and two oxygen atoms

• one silicon and four oxygen atoms

Heavy water is represented as

• H₂¹⁸O

• D₂O

• D₂¹⁸O

• H₂O at 4°C

Which compound is used in photography?

• Na₂SO₅

• Na₂S₂O₈

• Na₂S₂6

• Na₂S₂O₃

CH₃CH₂CH₃ $\stackrel{400-600°\mathrm{C}}{\to }$ X + Y

X and Y are

• hydrogen

• methane

• hydrogen

• ethylene

36.

In the equation

CrO${}_4^{2-}$ + SO${}_3^{2-} \to \mathrm{Cr}(\mathrm{OH}{)}_4^{-} + {\mathrm{SO}}_4^{2-}$

the oxidation number of Cr changes from

• +6 to +4

• +6 to +3

• +8 to +4

• +4 to +3

How many $\mathrm{\pi }$ bonds are present in naphthalene?

• 4

• 5

• 6

• 7

Which of the following will be easily nitrated?

• 

• 

• CH₃NO₂

• C₆H₅NO₂

In Kjeldahl's method of estimation of nitrogen, CuSO₄ acts as

• oxidising agent

• reducing agent

• catalytic agent

• hydrolysis agent

Sodium thiosulphate is a

• reducing agent

• oxidising agent

• complexing agent

• bleaching agent