Given are two statements one is labeled as Assertion A and other is labeled as Reason R.

Assertion A : Magnesium can reduce Al₂O₃ at a temperature below 1350°C, while above 1350°C aluminium can reduce MgO

Reason R : The melting and boiling points of magnesium are lower thatn those of aluminium.

In light of the above statements, choose most appropriate answer for the options given below

 $\frac{dE}{dT}$ is the temperature Co-efficient of cell. The cell having less variation of EMF, with respect to temperature have high efficiency.

In ores/mineral available earthy and undesired impurities are gangue

Sol. Reactivity towards ${\mathrm{A}\mathrm{g}\mathrm{N}\mathrm{O}}_3$  depend on stability of carbocation formed

Leaching involves the given reaction,

$4Au\left(s\right)+8C{N}^{-}\left(aq\right)+2H_{2}O\left(aq\right)+O_2\left(g\right)\to 4{\left[Au{\left(CN\right)}_2\right]}^{-}\left(aq\right)+4O{H}^{-}\left(aq\right)$              

Here, O₂ is required for formation of Au (l) cyanide complex but no complex in absence of O₂.

$2{\left[Au{\left(CN\right)}_2\right]}^{-}\left(aq\right)+Zn\left(s\right)\to {\left[Zn{\left(CN\right)}_4\right]}^{2-}\left(aq\right)+2Au\left(s\right)$                

In above displacement reaction, Zn is oxidized.

Higher the E.N. difference between hydrogen and other atom then higher be the strength of intermolecular H-bond

Here, order of difference in E.N is

O - H > N – H > C - H

Hence, correct order of H bond strength is,

CH₄ < HCN < NH₃