21.

Among the following, which is water insoluble?

• Sodium fluoride

• Potassium fluoride

• Beryllium fluoride

• Magnesium fluoride

Assertion (A) : A catalyst increases the rate of a reaction.

Reason (R) : In presence of a catalyst, the activation energy of the reaction increases.

The correct answer is

• Both (A) and (R) are true and (R) is the correct explanation of (A).

• Both (A) and (R) are true but (R) is not the correct explanation of (A).

• (A) is true, but (R) is not true

• (A) is not true, but (R) is true

Which of the following is not a peroxy acid ?

• Perphosphoric acid

• Pernitric acid

• Perdisulphuric acid

• Perchloric acid

Which of the following pair of transition metal ions, have the same calculated values of magnetic moment ?

• Ti²⁺ and V²⁺

• Fe²⁺ and Cu²⁺

• Cr²⁺ and Fe²⁺

• Co²⁺ and Ti²⁺

The formula of the product formed, when sodium thiosulphate solution is added to silver bromide is

• Ag₂S₂O₃

• Ag₂S

• Na₃[Ag(S₂O₃)₂]

• Ag₃[Na(S₂O₃)₂]

Which of the following statements is correct ?

• Silicon doped with boron is an n-type semiconductor

• Silicon doped with arsenic is a p-type semiconductor

• Metals are good conductors of electricity

• Electrical conductivity of semiconductors decreases with increasing temperature

Which one of the following noble gases is used in miner's cap lamps ?

• Helium

• Neon

• Argon

• Krypton

The following are some statements related to VA group hydrides,

(I) Reducing property increases from NH₃ to BiH₃

(II) Tendency to donate lone pair decreases from NH₃ to BiH₃.

(III) Thermal stability of hydrides decreases from  NH₃ to BiH₃.

(IV). Bond angle of hydrides decreases from  NH₃ to BiH₃.

The correct statements are:

• I, II, III and IV

• I, III and IV

• L, II and IV

• I and IV

Which of the following is an example of interstitial hydride?

• NH₃

• CH₄

• ZnH₂

• H₂O

Calculate the emf of the cell Cu(s)|Cu²⁺(aq)|| Ag⁺ (aq)| Ag(s). Given ${\mathrm{E}}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}^{°} = +0.34 \mathrm{V}, {\mathrm{E}}_{{\mathrm{Ag}}^{+}/ \mathrm{Ag}}^{°} = 0.80 \mathrm{V}$.

• +0.46 V

• +1.14 V

• +0.57V

• -0.46 V