21.

Which one of the following cannot form an amphoteric oxides?

• Al

• Sn

• Sb

• P

The weight in grams of a non-volatile solute (mol. wt. 60) to be dissolved in 90 g of water to produce a relative lowering of vapour pressure of 0.02 is

• 4

• 8

• 6

• 10

The experimentally determined molar mass of a non-volatile solute, BaCl₂ in water by Cottrell's method, is

• equal to the calculated molar mass

• more than the calculated molar mass

• less than the calculated molar mass

• double of the calculated molar mass

The emf (in V) of a Daniell cell containing 0.1 M ZnSO₄ and 0.01 M CuSO₄ solutions at their respective electrodes is

$({\mathrm{E}}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}^{°}= + 0.34 \mathrm{V}; {\mathrm{E}}_{{\mathrm{Zn}}^{2+}/ \mathrm{Zn}}^{°} = -0.76\mathrm{V})$

• 1.10

• 1.16

• 1.13

• 1.07

Which one of the following elements, when present as an impurity in silicon makes it a p-type semiconductor?

• As

• P

• In

• Sb

Which one ofthe following statements is correct for the reaction?

CH₃COOC₂H₅(aq) + NaOH(aq) → CH₃COONa (aq) + C₂H₅OH (aq)

• Order is two but molecularity is one

• Order is one but molecularity is two

• Order is one but molecularity is one

• Order is two but molecularity is two

The catalyst and promoter respectively used in the Haber's process of industrial synthesis of ammonia are

• Mo,V₂O₅

• V₂O_5, Fe

• Fe, Mo

• Mo, Fe

Gelly is a colloidal solution of

• solid in liquid

• liquid in solid

• liquid in liquid

• solid in solid

Bond energy of Cl₂, Br₂ and I₂ follow the order

• Cl₂ >Br₂ > I₂

• Br₂ >Cl₂ > I₂

• I₂ > Br₂ >Cl₂

• I₂ > Cl₂ >Br₂

Assertion (A): The boiling points of noble gases increases from He to Xe.

Reason (R): The interatomic van der Waals' attractive forces increases from He to Xe.

The correct answer is:

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

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

• (A) is true but (R) is not true.

• (A) is not true but (R) is true.