What drives spontaneous reactions?
select one:
a. decreasing enthalpy and decreasing entropy
b. decreasing enthalpy and increasing entropy
c. increasing enthalpy and decreasing entropy
d. increasing enthalpy and increasing entropy

option B

Explanation:

A spontaneous reaction drive favorable when enthalpy is decreasing and the entropy is increasing on the system. If that happens the reaction occurs spontaneously

b. decreasing enthalpy and increasing entropy

Explanation:

∆H stands for enthalpy change and ∆S stands for entropy change

Spontaneity depends on the enthalpy and entropy changes of the reaction

∆G = ∆H - T∆S

When ∆H is negative and ∆S is positive  

∆G will be negative

For a spontaneous reaction ∆G is negative

If ∆G = 0 then the reaction will be at equilibrium  

If ∆G is positive the reaction is non spontaneous.

Decreasing enthalpy (negative) and increasing entropy (positive) will give a negative number for

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%