Question

For which of the following processes will \DeltaΔS be negative?PbCl2(s) = Pb2+(aq) + 2 Cl-(aq)MgO(s) + CO2(g) = MgCO3(s)CO2(aq) = CO2(g)C5H12(l) + 8 O2(g) = 5 CO2(g) + 6 H2O(g)

Answer 1

a)
`PbCl_2(s)\rightarrow Pb^(2+)(aq)+2Cl^-(aq)`:
`\Delta S` = +ve

b)
`MgO(s)+CO_2(g)\rightarrow MgCO_3(s)`:
`\Delta S` = -ve

c)
`CO_2(aq)\rightarrow CO_2(g)`:
`\Delta S`= +ve

d)
`C_5H_(12)(l)+8O_2(g)\rightarrow 5CO_2(g)+6H_2O(g)`:
`\Delta S` = +ve

Step-by-step explanation:

Entropy is the measure of randomness or disorder of a system. If a system moves from an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.

a)
`PbCl_2(s)\rightarrow Pb^(2+)(aq)+2Cl^-(aq)`

As solid is moving to ions form , randomness increases and thus sign of
`\Delta S` is positive.

b)
`MgO(s)+CO_2(g)\rightarrow MgCO_3(s)`

As gaseous reactants are converted to solid products , randomness decreases and thus sign of
`\Delta S` is negative.

c)
`CO_2(aq)\rightarrow CO_2(g)`

As liquid is changing to gas randomness increases and thus sign of
`\Delta S` is positive.

d)
`C_5H_(12)(l)+8O_2(g)rightarrow 5CO_2(g)+6H_2O(g)`

As 8 moles of gaseous reactants are converted to 11 moles of gaseous products , randomness increases and thus sign of
`\Delta S` is positive.