A 1.0 M solution of NaCl has a final concentration of 0.20 M and a final volume of 200 mL, what was the initial volume of the NaCl solution in mL?

Can someone me with questions 15 to 17 plz.

Word equation for k(s)+h2o(l) yield koh(aq) + h2(g)

The graph indicates the running route for tobias. which best describes his run? from time 0 to 6, he went fast and then slowed down. from time 6 to 10, he was at his slowest. from time 12 to 14, he went very slow. from time 14 to 18, he went toward the starting point.