Determine which choice(s) is/are correct?

i. stirring slows down (decreases) rate of dissolution.
ii. grinding solids increases their surface area of contact.
iii. heating slows down (decreases) rate of dissolution.
iv. grinding solids speeds up their rate of dissolution.
a) i, ii, and iii
b) ii and iv
c) i and iii
d) iii and iv

2 and 4 so B) II and IV

Explanation:

I false ... stirring speeds up the rate of dissolution because it increases surface area . II is true , III false ... heating up speeds up the rates of dissolution , IV is true .

b

Explanation:

usatestprep

"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."

the answer is b. dilution