231.

Heavy water is represented as

• H₂¹⁸O

• D₂O

• D₂¹⁸O

• H₂O at 4°C

The most abundant element in the universe is thought to be

• carbon

• oxygen

• hydrogen

• nitrogen

The compound that can work both as an oxidising as well as reducing agent is

• KMnO₂

• H₂O₂

• Fe₂(SO₄)₃

• K₂Cr₂O₇

Which one of the following is not a method to remove permanent hardness of water?

• Clark's method

• Calgon method

• Ion- exchange method

• Synthetic resins methods

Reaction of calgon with hard water containing Ca²⁺ ions produce

• [Na₂CaP₆O₁₈]^2-

• CaCO₃

• CaSO₄

• Ca₂(PO₄)₃

Diborane (B₂H₆) reacts independently with O₂ and H₂O to produce, respectively:

• B₂O₃ and H₃BO₃

• H₃BO₃ and B₂O₃

• B₂O₃ and [BH₄]^-

• HBO₂ and H₃BO₃

100 mL of a water sample contains 0.81 g of calcium bicarbonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of CaCO₃ is: (molar mass of calcium bicarbonate is 162 g mol^-1 and magnesium bicarbonate is 146 g mol^-1)

• 1,000 ppm

• 100 ppm

• 10,000 ppm

• 5000 ppm

Which of the following statement about hydrogen is incorrect?

• Hydrogen never acts as cation in ionic salts

• Hydronium ion, H₃O⁺ exist freely in solution

• Dihydrogen does not act as a reducing agent

• Dihydrogen does not act as a reducing agent

The reaction of aqueous KMnO₄ with H₂O₂ in acidic conditions gives.

• Mn⁴⁺ and O₂

• Mn²⁺ and O₂

• Mn²⁺ and O₃

• Mn²⁺ and O₃

A hydrogen gas electrode is made by dipping platinum wire in a solution of HCl of pH =10 and by passing hydrogen gas through the platinum wire at 1 atm pressure. The oxidation potential of electrode would be

• 0.0591 V

• 0.59 V

• 0.118 V

• 0.118 V