81.

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

Moist hydrogen peroxide can not be dried over conc. H₂SO₄ because

• it can catch fire

• it is reduced by H₂SO₄

• it is oxidised by H₂SO₄

• it is decomposed by H₂SO₄

Glauber's salt is

• Na₂SO₄.10H₂O

• Na₂S₂O₃.5H₂O

• CuSO₄.5H₂O

• Na₂B₄O₇.10H₂O

Hydrogen molecule differs from chlorine molecule in the following respect.

• Hydrogen molecule is non-polar but chlorine molecule is polar

• Hydrogen molecule is polar while chlorine molecule is non-polar

• Hydrogen molecule can form intermolecular hydrogen bonds but chlorine molecule does not

• Hydrogen molecule cannot participate in coordinate bond formation but chlorine molecule can

Which of the following undergoes reduction with hydrogen peroxide in alkaline medium?

• Mn²⁺

• I₂

• PbS

• Fe²⁺

CaC₂ and H₂O react to produce

• CH₄

• C₂H₄

• C₂H₂

• C₂H₆