The flask would feel cooler than when the reaction first started.
At STP, or standard temperature and pressure, 1 mol of any gas will take up 22.4 liters of space. Assuming STP, 4.5 moles of H2 will take up 100.8L.
It would have a zero charge because it is a neutral atom. The number of electrons which is a negative charge is equal to the number of protons which is positive, they will cancel each other out hence meaning it will become neutral
