What is the mass of 5489 moles of selenium

Which diagram shows the correct way to represent an ionic compound of magnesium oxide?

Iron (3) oxide will decompose in the presence of hydrogen gas and heater to produced iron and digydrogen monoxide white a balanced chemical equation

You open a can of soda at room temperature and hear a hiss. which of the following factors has changed inside the container? a.) atmospheric pressure b.) temperature of gas c.) type of gas d.) amount of gas