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Explain which of the following reactions will occur. a.overset (RCOOH) underset (pK_(a)=5) + overset (HCO_(3)^(-) underset (pK_(a)=10.3) rarr b.RCOOH + CO_(3)^(2-) rarr c.overset (PhOH) underset (pK_(a)=10) + HCO_(3)^(-) rarr d.PhOH + CO_(3)^(2-) rarr e.RCOO^(-) + overset (CO_(2)+H_(2)O) underset (pK_(a)=6.4) rarr f.PhO^(-) + CO_(2) + H_(2)O rarr g.RSH + O^(-)H rarr h.ROH + O^(-)H rarr i.ROH + RS^(-) rarr j.RSH + RO^(-) rarr |
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Answer» Solution :The acid-base equilibrium reaction favours the side with weaker acid `(W_(A))` and weaker base `(W_(B))`. If the weaker acid is on the RIGHT side, the reaction occurs, but if the weaker acid is on the left side, the reverse reaction occurs. a.The reaction is: `OVERSET (RCOOH) underset (pK_(a)=5)` + `overset (HCO_(3)^(-)) underset (pK_(a)=10)` `rarr` `overset (RCOO^(-)) underset (Weaker conjugate base (C_(B))` + `overset (H_(2)O+CO_(2)) underset (W_(A)(pK_(a)=6.4))` b.Reaction occurs `RCOOH + CO_(3)^(2-) rarr` `overset (RCOO^(-)) underset (WC_(B))` + `overset (HCO_(3)^(-)) underset (pK_(a)=10.3 W_(A))` c.  this reaction occurs if any substituted phenol that has `pK_(a) gt 10.5` does not react,e.g.,  e.  f. Reaction occurs. `PhO^(-) + `overset (H_(2)O + CO_(2)) underset pK_(a)=6.4)` `rarr` `overset (PhOH) underset (W_(A)pK_(a)=10)` + `HCO_(3)^(-)` g. Reaction occurs. RSH is a stronger acid than `H_(2)O`, and ROH.Therefore, `RS^(-)` is a weaker base than `O^(-)H` and `RO^(-)`. h.Reverse reaction occurs. `overset (ROH + O^(-)H) underset (W_(A)W_(B))`  `overset (RS^(-) + H_(2)O) underset _(S_(B)S_(A))` (Alcohols are weaker ACIDS than OH and `H_(2)O`, and `RO^(-)` is stronger base than `O^(-)H`.) However, the DIFFERENCES in acidities and basicities are small and all species are present in equilibrium. i.Reverse reaction occurs. `overset (ROH + RS^(-)) underset (W_(A)W_(B))``RSH + RO^(-)) underset (S_(A)S_(B))` RSH (thiols) are stronger acids than ROH, and `RO^(-)` is a stronger base than `RS^(-)`. j.Reaction occurs. `overset (RSH + RO^(-)) underset (S_(A)S_(B))``rarr``overset (RS^(-) + ROH) underset (W_(B)W_(A))` |
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