Given the equation N2(g) +3H2 (g)--> 2NH3 (g)
1 mole of N2 gas is needed to completely react with 3 moles of H2 gas.
How many molecules of H2 gas are needed?

#"6 moles"#

Explanation:

Take a look at the balanced chemical equation for this synthesis reaction

#"N"_text(2(g]) + color(red)(3)"H"_text(2(g]) -> 2"NH"_text(3(g])#

Notice that you have a #1:color(red)(3)# mole ratio between nitrogen gas and hydrogen gas. This means that, regardless of how many moles of nitrogen gas you have, the reaction will always consume twice as many moles of hydrogen gas.

So, if you have #2# moles of nitrogen taking part in the reaction, you will need

#2color(red)(cancel(color(black)("moles N"_2))) * (color(red)(3)" moles H"_2)/(1color(red)(cancel(color(black)("mole N"_2 = "6 moles H"_2#

your parents i think this could be it