Water is produced from the reaction of hydrogen and oxygen gas, according to the equation below. What is the excess reactant in the reaction of 4.2 moles of hydrogen with 3.0 moles of oxygen? 2H2(g) + O2(g) = 2H2O(L)

Select one:
a. Water
b. Oxygen
c. No excess reactant
d. Hydrogen

Explanation:

Mole ratio of Oxygen to Hydrogen gas = 1 : 2.

If we use 3.0 moles of oxygen gas, we would need 3.0 * 2 = 6.0 mol of hydrogen gas.

However we only have 4.2 mol of hydrogen. Therefore hydrogen is limiting and oxygen is in excess. (B)

"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."