How much heat is produced when 1.25 g of chromium metal reacts with oxygen gas under standard conditions?

Explanation:

Hello,

In this case, the undergoing chemical reaction is:

In such a way, we compute the corresponding yielded moles of chromium (III) oxide by stoichiometry:

Now, since this is about a formation reaction, the standard enthalpy of formation accounts for the released heat during this reaction, which is:

Finally, as we computed the yielded moles, we compute the associated produced heat via:

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"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."