Explain why the following reaction, although thermodynamically feasible, does not take place at ordinary temperature.
`Cr_(2)O_(3)(s)+2Al(s)rarrAl_(2)O_(3)(s)+Cr(s),`
`DeltaG^(@)=-421kJ`

Explain the following: The reduction of Cr_2O_3 with AI is thermodynamically feasible yet it does not occur at room tem-perature.

Althrough thermodynamically feasible, mangesium metal cannot be used for the reduction of Al_(2)O_(3) - why?

Identify the following half -reactions as oxidantion half-reactions and reduction half -reactions : Cr_(2)O_(7)^(2-)to2Cr^(3+)

Explain why the following S_(N)2 reactions do not take place: (ii) Cl^(Theta)+CH_(3)OCH_(3) to CH_(3)Cl+CH_(3)O^(Theta)

In aluminium extraction by the Bayer process, alumina is extracted from banxite by sodium hydroxide at height temperatures and pressures Al_(2)O_(3)(s) + 2OH^(-) (aq) rarr 2Al_(2)O_(2)^(-) (aq) + H_(2)O (l) Solid impurities such as Fe_(2)O_(3) and SiO_(2) are removed and then Al(OH)_(4)^(-) is reprecipitated: 2Al(OH)_(4)^(-) rarr Al_(2)O_(3).3H_(2)O(s) + 2OH^(-) (aq). In the industrial world.

Identify whether the following reactions are redox reactions or not : 2HgO(s)to2Hg(l)+O_(2)(g)

For the reaction ,2S_(2)O_(4)^(2-)+1_(2)toS_(4)O_(6)^(2-)+2I^(-) -

Balance the reaction by ion-electrons mehod : Cr_(2)O_(7)^(2-)+C_(2)O_(4)^(2-)H^(+)toCr^(3+)+CO_(2)H_(2)O

In the following redox reactions, identify the oxidation half -reactions and reduction half -reactions along with the oxidants and and reductants. 2Na_(2)S_(2)O_(3)(aq)+I_(2)(s)toNa_(2)S_(4)O_(6)(aq)_+2NaI(aq)