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

To calculate Delta S surroundings, use the equation Delta S₀ surroundings = (-Delta H rxn) / T. For the example given, Delta S₀ surroundings at 298 K would be 949 J/K. Delta S sys is found using standard entropy values and the balanced chemical equation.

Step-by-step explanation:

To calculate the change in entropy of the surroundings (Delta S surroundings) for a reaction, you may use the relation that links enthalpy change (Delta H rxn) of the system and the absolute temperature (T) at which the reaction takes place. The formula is as follows:

Delta S₀ surroundings = (-Delta H rxn) / T

For the given reaction with Delta H rxn = -283 kJ and T at 298 K, the calculation would be:

Delta S₀ surroundings = (-(-283 kJ)) / (298 K) = 0.949 kJ/K

To express this value in the standard SI units of J/K, multiply it by 1000:

Delta S₀ surroundings = 0.949 kJ/K × 1000 = 949 J/K

As for calculating the entropy change of the system (Delta S sys), you would generally use standard entropy values and apply them to the balanced chemical equation. The formula to calculate Delta S sys is given by:

Delta S sys = ΣS°(products) - ΣS°(reactants)

Answer 2

949.66J

Step-by-step explanation:

ΔS(surr)= -ΔHsys/t

ΔHrxn=ΔHsys

ΔHsys= -283KJ

-ΔHsys=283KJ

283KJ/298K=0.94966KJ

1KJ=1000J

0.94966KJ*1000=949.66J

ΔS(sys= sum of ∘ products - sum of ∘ reactants

∘ you will have to look up as they verry from chemical to chemical

if you have more than 1 mol of a product or reactant you have to make sure you have multiply the ∘ by the number of moles for example

2 H2 + O2 = 2 H20

∘ H2= 130.7

∘ O2= 205.2

∘H20=188.8

ΔS(sys= 2(188.8) - [2(130.7)+ 205.2]

ΔS(sys= 377.6- (261.4+205.2)

ΔS(sys= 377.6- 466.6= -89

ΔS(sys=-89