EARTH SCIENCE: PLEASE HELP ME !!! Which tools do astronomers use to determine the effects of collisions between galaxies? Select the two correct answers.(1 point) computer simulations

print encyclopedia entries

space telescopes

solar system models

Iwill give extra points to who gets this right

Which best describes why nh4+ can form an ionic bond with ci-?

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.)