An unknown gas at 47.1 celsius and 1.10 atm has a molar mass of 16.04 g/mol. Assuming ideal behavior, what is the density of the gas

When balancing a chemical equation:

How many moles of sulfur dioxide are produced when 4.38 moles of oxygen completely react with iron (iv) sulfide

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