What is this? I have know idea

What is the mass of 0.46 mil of mgcl2

Which element is least likely to undergo a chemical reaction

What is conserved in the reaction shown below? h2(g) + cl2 (g) --> 2hcl(g)a. mass onlyb. mass and moles onlyc. mass, moles, and molecules onlyd. mass, moles, molecules, and volume