21.

Among the following the least thermally stable is

• K₂CO₃

• Na₂CO₃

• BaCO₃

• Li₂CO₃

Green chemistry means such reactions which

• produce colour during reactions

• reduce the use and production of hazardous chemicals

• are related to the depletion of ozone layer

• study the reactions in plants

Name the type of the structure of silicate in which one oxygen atom of [SiO₄]^4- is shared?

• Sheet silicate

• Pyrosilicate

• Three dimensional silicate

• Linear chain silicate

Which one of the following is present as an active ingredient in bleaching powder for bleaching action?

• Ca(OCl)₂

• CaO₂Cl

• CaCl₂

• CaOCl₂

A solution with negative deviation among the following is

• ethanol-acetone

• chlorobenzene-bromobenzene

• chloroform-acetone

• benzene-toluene

Observe the following reaction

2A + B $\to$ C

The rate of formation of C is 2. 2 x 10^-3 mol L^-3 min^-1. What is the value of $-\frac{\mathrm{d}\left[\mathrm{A}\right]}{\mathrm{dt}}$ (in mol L^-1 min^-1)?

• $2.2 \times {10}^{-3}$

• $1.1 \times {10}^{-3}$

• $4.4 \times {10}^{-3}$

• $5.5 \times {10}^{-3}$

If x is amount of adsorbate and m is amount of adsorbent, which of the following relations is not related to adsorption process?

• $\frac{x}{m} = \mathrm{f}\left(T\right) \mathrm{at} \mathrm{constant} p$

• $p = \mathrm{f}\left(\mathrm{T}\right) \mathrm{at} \mathrm{constant} \left(\frac{x}{m}\right)$

• $\frac{x}{m} = p \times \mathrm{T}$

• $\frac{x}{m} = \mathrm{f}\left(\mathrm{p}\right) \mathrm{at} \mathrm{constant} \mathrm{T}$

Standard electrode potential of three metals X, Y and Z are -1.2 V, +0.5 V and -3.0 V respectively. The reducing power of these metals will be

• Y > X > Z

• Z > X > Y

• X > Y > Z

• Y > Z > X

Percentage of free space in a body centre cubic unit cell is

• 30%

• 32%

• 34%

• 28%

Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of

• Cr${\mathrm{O}}_4^{2-}$

• Cr₂(SO₃)₃

• CrSO₄

• Cr₂(SO₄)₃