Plsss help ASAP Dont guess

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

At stp, which substance is the best conductor of electricity? a. nitrogen b. neon c. sulfur d. silver

Mercury metal is poured into a graduated cylinder that holds exactly 22.5 ml the mercury used to fill the cylinder mass in 306.0 g from this information calculate the density of mercury