acs enrgetics? + others

[Philippines03j]

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My question comes from the energetics chapter #5 of the practice problems. (Pg49)

When Na2s2o3 x3h20 dissolves in water, the solution gets cold. Which diagram best represents the change in enthalpy for contents of the flask?

I know that as something disolves it will increase in entropy and also has a positive entrapy. But can someone explain how I would decide between graph A and graph D. I am sure it is simple but...

Thanks!🙂

Also can someone confirm that the following is either right or wrong?

1. When using Bond energies, subtract products from the reactants which gives the final. (R-P= Final)

2. When dealing with Enthalpy (H) subtract reeactants from the products.
(P-r= H)

Thanks!