Question

In which of the following reactions is work done by the system to the surroundings?

A) 2CH3OH(l) + 3O2(g) --> 4H2O(l) + 2CO2(g)

B) S(s, rhombic) + O2(g) --> SO2(g)

C) 2AgNO3(s) --> 2AgNO2(s) + O2(g)

D)4Fe(s) + 3O2(g) --> 2Fe2O3(s)

My guess is B because according to w = -PΔV, the gas would be expanding in that equation and would cause work to be done on the surroundings. However, I am still a little confused and not sure if it is correct.

Answer 1

I agree that it is B, however, I could most definitely be wrong.

Answer 2

I disagree with both of you.

A) 2CH3OH(l) + 3O2(g) --> 4H2O(l) + 2CO2(g)

<b> 3 mols gas goes to 2 mols. Not expanding so it isn't A.</b>

B) S(s, rhombic) + O2(g) --> SO2(g)

<b> Can't be B. 1 mols gas on left goes to 1 mol gas on the right. Volume stays the same. Not expanding. </b>

C) 2AgNO3(s) --> 2AgNO2(s) + O2(g)

<b>Must be C. Zero gas mols on the left to 1 mol gas on the right. Expanding. Yes, doing work on surroundings.</b>

D)4Fe(s) + 3O2(g) --> 2Fe2O3(s)

<b>Can't be D. 3 mols gas on left to zero on the right. Not expanding.</b>