For each of the reactions at constant pressure, determine whether the system does work on the surroundings, the surroundings does work on the system, or essentially no work is performed.

(a) 4Fe + 3O2 --> 2Fe2O3
(b) 2H2O2 --> O2 + 2H2O

Explanation:

When work is done then there will occur change in volume. And, most change in volume occurs when there will be production of gas is taking place. We assume that no work is done when no gas is produced.

(a)   For

Here, 3 moles of gas is producing 0 moles of gas. This means that work is done on the system.

(b)  And, more is the production of a gas taking place in a reaction more will be the amount of work done by the system.

For

Here, 2 moles of a gas is producing 3 moles of a gas. Since, gas is increasing so, work will be done by the system.

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."