Calculate the number of moles of gas in the following at STP: 45.6 L of H2 gas

Ineed ! i have no clue how to do this problem.

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

How do dying stars contribute to the formation of planets