30. Which of the following atoms would form a trivalent anion?
A. Aluminium
B. Oxygen
C. Lithium
D. Nitrogen​

5. how can you decrease the pressure of a gas in a container without changing the volume of the gas?

An empty fuel tank can still contain and therefore can be even more dangerous than one full of liquid fuel.

How many liters of oxygen gas, at standard temperature and pressure, will react with 35.8 grams of iron metal? 4 fe (s) + 3 o₂ (g) → 2 fe₂o₃ (s)