What is it about the structure of magnesium atoms that makes them react more slowly than calcium atoms?

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

Which statement is true about hcl? (5 points) select one: a. it is a salt because it increases the concentration of metallic ions. b. it is a salt because it is formed by the reaction of an acid and a base. c. it is an acid because it increases the concentration of hydroxyl ions. d. it is an acid because it increases the concentration of hydronium ions.

What is the percent by mass of oxygen in fe2o3