HELP CHEM IM GIVING BRAINLIST

Find the mass in grams of hydrogen gas produced when 14.0 moles of hcl is added to an excess amount of magnesium.

Asample of silver (with work function ? = 4.52 ev) is exposed to an ultraviolet light source (? = 200 nm), which results in the ejection of photoelectrons. what changes will be observed if: silver is replaced with copper (? = 5.10 ev) more photoelectrons ejected no photoelectrons are emitted fewer photoelectrons ejected more energetic photoelectrons (on average) less energetic photoelectrons (on average)

When an object falls through the air and encounters air resistance its overall speed will be than if it had not encountered air resistance? (one word answer)