A 13.79 gram sample of cobalt is heated in the presence of excess sulfur. A metal sulfide is formed with a mass of 21.29 g. Determine the empirical formula of the metal sulfide. Enter the elements in the order Co, S

empirical formula:

Iknow the answer is a but i don't know why

If a solution contains 3 moles/liter of sodium chloride (nacl, made of sodium ions and chloride ions), what is the osmolarity of this solution

The equation below shows the reaction of zinc with hydrochloric acid (hcl). zn (s) + 2 hcl (aq) —> zncl2 (aq) + h2 (g) what will happen if the concentration of hcl is decreased? a. more zncl2 will be produced. b. the reaction rate will slow down. c. the hydrochloric acid will become more acidic. d. the reaction will produce water instead of hydrogen gas.