During a lab experiment, students are supposed to add small pieces of magnesium, aluminum, and calcium metal to concentrated hydrochloric acid in a test tube. The laboratory instructions include strong safety warnings to make sure that no sparks, open flames, or high heat sources are present in the room when students perform this experiment. Which is the most likely reason for these warnings?

Hydrogen gas is highly flammable.

Heat may cause the hydrochloric acid to break down.

Heat can cause the acid to produce a salt.

The zinc within a copper-plated penny dissolves in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can reach the zinc). the reaction between the acid and the zinc 2h+(aq)+zn(s)→h2(g)+zn2+(aq) . when the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 °c is 0.947 l at a total pressure of 743 mmhg . (vapor pressure of water is 23.78 mmhg at 25 °c .) what mass of hydrogen gas is collected? answer in appropriate significant figures