Which one of the following molecular hydrides acts as a Lewis acid? 

• NH₃

• H₂O

• B₂H₆

• B₂H₆

Some statement about heavy water are given below

A) Heavy water is used as a moderator in nuclear reactors.

B) Heavy water is more associated than ordinary water.

C) Heavy water is more effective solvent than ordinary

• A and B

• A, B and C

• B and C

• B and C

In which case is a number of molecules of water maximum?

• 18 mL of water

• 0.18 g of water

• 10^-3 mol of water

• 0.00224 L of water vapours at 1 atm and 273K

Which one of the following reactions does not form gaseous product?

• PbO₂ + H₂O₂ $\to$

• Acidified KMnO₄ + H₂O₂ $\to$

• PbS + H₂O₂ $\to$

• Cl₂ + H₂O₂ $\to$

$$\begin{gathered} {\mathrm{SF}}_4 \stackrel{\mathrm{Hydrolysis}}{\to } \mathrm{X} +\hspace{0.17em}\mathrm{Y} \\ \mathrm{X} + {\mathrm{H}}_2\mathrm{S} \to \mathrm{Z} \end{gathered}$$

Here, Z is

• SO₃

• colloidal sulphur

• gaseous sulphur

• solid sulphur

246.

Which of the following atomic and physical properties of hydrogen is false?

• Hydrogen > Deuterium > Tritium; (melting point/ K)

• Hydrogen < Deuterium < Tritium; (boiling point/ K)

• Hydrogen < Deuterium < Tritium; (density /gL^-1)

• Hydrogen > Deuterium > Tritium; (% relative abundance)

When H₂O₂ is added to ice cold solution of acidified potassium dichromate in ether and the contents are shaken and allowed to stand

• a blue colour is obtained in ether because of formation of CrO₅

• a blue colour is obtained in ether because of formation of CrO₃

• a blue colour is obtained in ether because of formation of Cr₂(SO₄)₃

• chromyl chloride is formed

500 mL of a sample of water required 19.6 mg of K₂Cr₂O₇ for the oxidation of dissolved organic matter in it in the presence of H₂SO₄. The COD of water sample is

• 3.2 ppm

• 7.2 ppm

• 6.4 ppm

• 4.6 ppm

Number of hydrogen-bonded water molecules associated in CuSO₄.5H₂O is

• one

• two

• three

• All the five

Excess fluoride (over 10 ppm) in drinking water can cause

• harmful effect of bones and teeth

• methemoglobinemia

• kidney damage

• laxative effect