[baseg_18]

If 75.5 g of aluminum react with excess hydrochloric acid (hydrogen chloride), how much hydrogen gas will be produced in a single displacement reaction?

If it's not too much trouble can someone please explain the steps to solve this reaction problem, so that I can do these problems on my own.

Thanks,
Baseg_18

[tamim83]

Well the first thing you need is a chemical equation.  With problems like this that already does not give you one, you always want to start out with an equation.  Remember to balance this equation too so that you have proper molar relationships (I'll leave this up to you to figure out  ) After that, it is a fairly straight foward stoiciometry problem.  Convert the mass of Al to moles and use your balanced chemical equation to convert from moles of Al to moles of H₂.  Then you can convert your moles of H₂ to grams. 

[kayamusty]

Al + HCl -------- AlCl3  +  3/2 H2

use this equation

[baseg_18]

Quantum Kitten or anybody,

Is this the correct way to do this problem?:

1st step-
   Al + 2 HCl --> H2 + AlCl
(75.5 g)

2nd step-
 75.5g Al * (1 mol Al)(1 mol H2) / (26.98g Al)(1 mol Al)

3rd step
75.5 g * (1 mol Al)(1 mol H2)(22.4 L H2) / (26.98g Al)(1 mol Al)(1 mol H2) = 62.6 L or 62.6 dm^3

Is the answer 62.6 dm^3?

[wereworm73]

You need to use this balanced equation:

Al + 3 HCl ---> AlCl₃ + 3/2 H₂
(Aluminum is trivalent so it bonds with three chloride ions to form AlCl₃)


Then you figure out how many moles of Al are in 75.5 g and then just multiply that number by 3/2 (because by the balanced equation above, you get 3/2 moles of H₂ for every mole of aluminum).  Then you'll have the number of moles of H₂ gas.  If you need the amount of hydrogen expressed in liters, just multiply by 22.4 L/mol (assuming the pressure is 1 atm).

[baseg_18]

so would I multiply 62. 6 dm^3 * 1.5 (3/2) to get the answer 93.9 dm^3 ?

[baseg_18]

I think I finally got it!

2.798 moles of Al * 1.5 = 4.197

4.197 * 22.4 = 94.0128

Thank you Wereworm73, Kayamusty, and Tamim83 for all your help.

[tamim83]

I think I finally got it!

2.798 moles of Al * 1.5 = 4.197

4.197 * 22.4 = 94.0128

Looks great!! 

Thank you Wereworm73, Kayamusty, and Tamim83 for all your help.

No problem