Question

Determine the entropy change for the following displacement reaction. .
Cl2(G) + PbBr2 (AQ) yields PbCl2 (AQ) + Br2 (L)

Answer 1

Natalie, is that it? No more data?The entropy will decrease, gas + liquid goes to liq + liq.

Answer 2

To find the entropy change of a reaction, we subtract the sum of the entropies of the reactants from the sum of the entropies of the products.

delta S = (entropy of products) - (entropy of reactants)

in plain english, the balanced reaction equation says that per mole of reaction, we are converting:

one mol of Cl2 plus 1 mol of lead bromide -> 1 mol of Br2 plus 1 mol of lead chloride.

because the question doesn't say much more, i am just going to assume--as usual--that the reactants are initially in standard states and the products end up in their standard states. then we can plug in the tabulated standard molar entropies. be careful, these are molar quantities.

so the entropy of products = 1 mol * S0(PbCl2,aq) + 1 mol * S0(Br2,aq)

and the entropy of reactants = 1 mol * S0(PbBr2,aq) + 1 mol * S0(Cl2,g)

the S0's are the standard molar entropies found in handbooks.

finally, the standard entropy change for the reaction is:

(entropy of products) - (entropy of reactants) / (1 mol of reaction)

so the unit is Joule per Kelvin per mole (of reaction).