[dunka]

Hello, I can't seem to get my head around this

calculate the mass of aluminium needed to generate 7.5 dm3 hydrogen gas by reastions with excess hydrochloric acid

This is just an example of a question. I dont need an answer but could you run me through how you would work this out.

[Borek]

Start with the reaction equation.

[dunka]

Start with the reaction equation.

So obviously 2Al + 6HCl --> 2AlCl₃ + 3H₂

[Arkcon]

Great.  Now the units of that equation is moles.  So 2 moles of aluminum is 3 moles of hydrogen gas.  But ..., how much mass of aluminum is that?  And how much space does that hydrogen gas take up?  You have some units conversions to do.

[Alexander Espino]

This is how you will do it,
1. Compute the number of moles hydrogen have in 1 cu dm, you can use idel gas law (PV=nRT)
2. Using stoichiometric ratio, compute for number of Al.
3. Compute the weight of Al needed using its molecular weight. W=n(MW)