Question

How to calculate delta S surroundings? calculate Delta S(surr) at the indicated temperature for a reaction having each of the following changes in enthalpy. the first problem is delta H rxn = -283 kJ; 298 K. can anyone walk me through this so i can do all of them? how do i calculate Delta S(sys)?

Answer 1

you can use the equation ΔS(surr)=q(surr)/T or ΔS(surr)=-q(rxn)/T.
the two equations are equal since we know that the energy the system (reactoin) puts out just goes into the surroundings.  
(In other words q(surr)=-q(rxn))

Using the equation, ΔS(surr)=-(-283kJ/298K)=0.9497kJ/K or 949.7J/K

This answer makes sense since the reaction is exothermic which means it released energy into the system which usually causes the entropy to increase.

I hope that helps.