¿Cuántos fotones de luz de frecuencia 5,5x10 15 Hz se necesitan para proporcionar 1000J de Energía?

What are the concentrations of hydroxide and hydronium ions in a solution with a ph of 10.2?

Modern pennies are composed of zinc coated with copper. a student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). the student puts the scratched penny in hydrochloric acid, where the following reaction occurs between the zinc and the hcl (the copper remains undissolved): zn(s) + 2 hcl(aq) → h2(g) + zncl(aq)the student collects the hydrogen produced over water at 25 °c. the collected gas occupies a volume of 0.899 l at a total pressure of 79 j mmhg. calculate the percent zinc (by mass) in the penny. (assume that all the zn in the penny dissolves.)

The number of neutrons is equal to the atomic number minus the atomic mass. a. true b. false