Zinc metal reacts with hydrochloric acid, HCl (aq), react to give hydrogen gas, H2 (g) and aqueous zinc chloride, ZnCl^2 (aq). A 0.4000 g sample of impure zinc fully reacts completely when added to 750.0 L of 0.0179 M HCl. After the reaction, the molarity of the solution has been reduced to 0.00403 M. What is the percent by mass of zinc in the sample?

Which statement best describes the relationship between period and frequency of light waves? a) in wave b the period increases and the frequency decreases from wave a. b) in wave a the period increases and the frequency decreases from wave b. c) in wave b the period is shorter and the frequency is greater than in wave a. d) in wave a the period is shorter and the frequency is greater than in wave b.

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.

Answer asap : ( a. how does mucus prevent the entry of pathogens? b. describe two ways white blood cells protect us from pathogens.