s- BLOCK JEE

In Zeolites and synthetic resin method, which will be more efficient in removing permanent hardness of water.

• Synthetic resin method as it exchanges only cation.

• zeolite resin method as it exchanges only cation.

• Synthetic resin method as it exchanges only anion.

• Synthetic resin is harmful to nature.

The first ionization potential of Na is 5.1 eV. The value of electron gain enthalpy of Na+ will be

1) -2.55 eV

2) -5.1 eV

3)-10.2 eV

4) +2.55 eV

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Several blocks of magnesium are fixed to the bottom of a ship to

• make the ship lighter

• prevent action of water and salt

• prevent puncturing by under-sea rocks

• keep away the sharks

The substance not likely to contain CaC0₃ is

• calcined gypsum

• sea shells

• dolomite

• a marble statue

A metal M readily forms its sulphate MS0₄ which is water soluble. It forms its oxide MO which becomes inert on heating. It forms an insoluble hydroxide M(OH)₂ which is soluble in NaOH solution. Then M is

(1) Mg

(2) Ba

(3) Ca

(4) Be

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K0₂(potassium super oxide) is used in oxygen cylinders in space and submarines. This is because it

(1) absorbs C0₂ and increases 0₂ content

(2) eliminates moisture

(3) absorbs C0₂

(4) produces ozone

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In curing cement plasters water is sprinkled from time to time. This helps in

(1) developing interlocking needle-like crystals of hydrated silicates.

(2) hydrating sand and gravel mixed with cement

(3) converting sand into silicic acid

(4) keeping it cool

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Amongst LiCl, RbCl, BeCl₂ and MgCl₂ the compounds with the greatest and the least ionic character, respectively are :

(1) RbCl and MgCl₂

(2) LiCl and RbCl

(3) MgCl₂ and BeCl₂

(4) RbCl and BeCl₂

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Hydrogen bomb is based on the principle of

(1) Nuclear fission

(2) Natural radioactivity

(3) Nuclear fusion

(4) Artificial radioactivity

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Which one of the following will react most vigorously with water?

(1) Li

(2) K

(3) Rb

(4) Na

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