Which one of the following ores is best concentrated by froth-floatation method ?

• Magnetite

• Cassiterite

• Galena

• Malachite

Excess of KI reacts with CuSO₄ solution and then Na₂S₂O₃ solution is added to it. Which of the statements is incorrect for this reaction ?

• Cu₂I₂ is formed

• CuI₂ is formed

• Na₂S₂O₃ is oxidised

• Evolved I₂ is reduced

The radioisotope, tritium (${}_1{}^3$H) has a half-life of 12.3 yr. If the initial amount of tritium is 32 mg, how many milligrams of it would remain after 49.2 yr ?

• 4 mg

• 8 mg

• 1 mg

• 2 mg

The method of zone refining of metals is based on the principle of

• greater noble character of the solid metal than that of the impurity

• greater solubility of the impurity in the molten state than in the solid

• greater mobility of the pure metal than that of impurity

• higher melting point of the impurity than that of the pure metal 

The correct order of ionic radii of Y³⁺, La³⁺, Eu³⁺ and Lu³⁺ is

(Atomic no. Y = 39, La = 57, Eu = 63, Lu = 71)

• Lu³⁺ < Eu³⁺ < La³⁺ < Y³⁺

• La³⁺ < Eu³⁺ < Lu³⁺ < Y³⁺

• Y³⁺ < La³⁺ < Eu³⁺ < Lu³⁺

• Y³⁺  < Lu³⁺ < Eu³⁺ < La³⁺

Which one of the following compounds, is not a protonic acid ?

• SO(OH)₂

• SO₂(OH)₂

• B(OH)₃

• PO(OH)₃

The mass of carbon anode consumed (giving only carbon dioxide) in the production of 270 kg of aluminium metal from bauxite by the Hall process is (Atomic mass of Al = 27)

• 180 kg

• 270 kg

• 540 kg

• 90 kg

Which of the following is anhydride of perchloric acid ?

• Cl₂O₇

• Cl₂O₅

• Cl₂O₃

• HClO

59.

When CH₂=CH-COOH is reduced with LiAlH₄, the compound obtained will be

• CH₃-CH₂-COOH

• CH₂=CH-CH₂OH
  

• CH₃-CH₂-CH₂OH

• CH₃-CH₂-CHO

Nylon threads are made of

• polyvinyl polymer

• polyester polymer

• polyamide polymer

• polyethylene polymer