# Chemistry

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Which of the following reactions are spontaneous (favorable)?
A] 2Mg(s) + O2(g) -> 2MgO(s) Delta G = -1137 kJ/mol ..
B] NH3(g) + HCl(g) -> NH4Cl(s) Delta G = -91.1 kJ/mol ...
C] AgCl(s) -> Ag+(aq) + Cl-(aq) Delta G = 55.6 kJ/mol ..
D] 2H2(g) + O2(g) -> 2H2O(g) Delta G = 456 kJ/mol
E] C(s) + H2O(l) -> CO(g) + H2(g) Delta G = 90.8 kJ/mol
F] CH4(g) + 2O2 -> CO2(g) + 2H2O(l) Delta G = -820 kJ/mol

I said that reaction A, B, and F were spontaneous because my book said spontaneity occurs when Delta G < 0 ... but theres also an example of a dissociation equation being spontaneous.. does that mean that reaction C is also spontaneous?

• Chemistry -

No. dG for C is >0; therefore, it is not spontaneous. What dissociation equation is listed as spontaneous.

• Chemistry -

Hello Dr. Bob,
This was the equation: 2N2O(g) ---> 2N2(g) + O2

• Chemistry -

I'm not sure I would call that a dissociation reaction. When I think of a dissociation reaction the AgCl ==>? Ag^+ + Cl^- is one; another one is CH3COOH ==> H^+ +CH3COO^-, NaCl + H2O => Na^+(aq) + Cl^-(aq), etc.
What you have written I call a reaction( specifically a decomposition) and not a dissociation. We would guess, by the way, that the decomposition of NO2 to N2 and O2 is spontaneous because the reverse reaction is NOT spontaneous. If it were, there wouldn't be much O2 around in the atmosphere for us to breathe.

• Chemistry -

Ohhh.. my mistake I understand now. thanks!

• Chemistry -

Which of the following reactions are spontaneous (favorable)?

A. DHAP ---> glyceraldehyde - 3 - phosphate ΔG=3.8 kJ/mol
B. C2H4+H2 ----> C2H6 ΔG=-150.97kJ/mol
C. C4H4O5 ---> C4H2O4+H2O ΔG=3.1 kJ/mol