For a reaction, `aA+bBhArrcC+dD`, the reaction quotient `Q=([C]_(0)^(c)[D]_(0)^(d))/([A]_(0)^(a)[B]_(0)^(b))`, where `[A]_(0)`, `[B]_(0)`, `[C]_(0)`, `[D]_(0)` are initial concentrations. Also `K_(c)=([C]^(c)[D]^(d))/([A]^(a)[B]^(b))` where `[A]`, `[B]`, `[C]`, `[D]` are equilibrium concentrations. The reaction proceeds in forward direction if `Q lt K_(c)` and in backward direction if `Q gt K_(c)`. The variation of `K_(c)` with temperature is given by: `2303log(K_(C_(2)))/(K_(C_(1)))=(DeltaH)/(R)[(T_(2)-T_(1))/(T_(1)T_(2))]`. For gaseous phase reactions `K_(p)=K_(c)(RT)^(Deltan)` where `Deltan=` moles of gaseous products `-` moles of gaseous reactants. Also `-DeltaG^(@)=2.303RT log_(10)K_(c)`. (`B`) The moisture content of a gas is often expressed as dew point, the temperature at which if gas is cooled becomes saturted with vapour pressure of water at that temperture. Dew point of `H_(2)O` is `43^(@)C` having vapour pressure `0.07 "torr"`. `CaCl_(2)*2H_(2)O_((s))hArrCaCl_(2(s))+2H_(2)O_((g))`, The equilibrium constant should not be more than..... `(atm)^(2)` if `CaCl_(2)` is to be used as desiccant.A. `8.5xx10^(-9)`B. `8.5`C. `8.5xx10^(-3)`D. `4.9xx10^(-3)`