4. When the mole fraction of solute is 1, there is (a) a 1:1 ratio of solute to solvent.
(b) no solute present.
(c) only solute present.
(d) only solvent present.
(e) 1 mole of solute and 99 moles of solvent.

(c) only solute present

Explanation:

In chemistry, the mole fraction, denoted by X, refers to the number of moles of a substance in a compound/mixture divided by the total number of substances in the same compound or mixture.

In this case, we can say that mole fraction represents the number of solutes to the number of solutes and solvent in the solution i.e. X = nA/nA + nB

Where; nA = number of solutes

nB = number of solvent

X = mole fraction.

Based on this analogy, When the mole fraction of solute is 1, there is only solute present. That is; X = 1 / 1 + 0

X = 1/1 = 1.

"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."