Which statements explain the shape of the titration curve observed in lab?
i. initially, the conductivity is zero since the reaction has not begun.
ii. during the reaction, the conductivity decreases due to the increase of ba+2 and oh– ions.
iii. at the equivalent point, the conductivity is nearly zero since all the ba+2 and oh– ions have reacted to produce nonelectrolyte products.
iv. after the endpoint, the conductivity increases due to the excess titrant.

II and IV

Explanation:

I - The conductivity is not zero because there are ions of the analyte in the solution.

II - This is correct, since the ions Ba+2 and OH- form BaOH that is insoluble, the conductivity decreases.

III - At the equivalent point the conductivity will have a quick increase of the conductivity.

IV - This is correct, after the endpoint, the tritant will not react, that will increase it's concentration, increasing the ions in the solution therefore the conductivity.

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).