How many neutrons would be in an atom of Selenium if the mass number for this particular isotope is Se-80?

If 90.0 grams of ethane reacted with excess chlorine, how many grams of dicarbon hexachloride would form

What is the molar mass of the anhydrous compound? answer using four significant figures. 36.02 g/mol 120.15 g/mol 156.12 g/mol

Rank the four gases (air, exhaled air, gas produced from from decomposition of h2o2, gas from decomposition of nahco3) in order of increasing concentration of co2