Solid aluminum reacts with HCL according to the following balanced equation at STP: 2AL(s)+6HCL(aq), how many liters of H2 gas are generated?

Question

Please help, these were the answers, which is right?

A.12.5L

B.15.2L

C.16.8L

D.14.8L

Answer 1

It seems that your question is missing something. How much aluminum is reacting with the HCl? The amount in grams will affect our answer. I can take you through the steps however, so you can simply plug in the value at the end.

The first thing to note is that at STP, 1 mol of gas fills 22.4 liters. For a problem like this, we need to go through three steps:

1) Write out and balance the full reaction equation

2) Determine how many moles of H₂ gas is formed by the reaction using the result of step 1 and some stoichiometry

3) Calculate the number of liters of H₂ gas formed using the result of step 2

Let's begin!

Step 1: The Reaction

We are given the following reactants: 2Al(s) + 6HCl(aq). We know that H₂ must form, and since aluminum acts as a cation with charge +3 and chlorine acts as an anion with charge -1, they will be attracted to each other and react to give aluminum chloride (AlCl₃, with three negative Cl charges to balance the the single positive three charge of the Al). Thus, our products must be H₂ and AlCl₃. We now must balance our reaction; since there are 2Al in the reactants, we need two in the products - so place a 2 in front of the AlCl₃. This conveniently balances the number of chlorines, since 2(3)=6 which is the number of chlorines in the reactants. Finally, we need 6 hydrogens as well - since we are forming H₂, and 2*3=6, we need three H₂. Thus our final, balanced reaction equation is:

2Al(s) + 6HCl(aq) --> 3H₂(g) + 2AlCl₃(aq). Awesome!

Step 2

Here's where we need the information - for now, I'll say that x grams of Al are used. Using stoichiometry:

x g Al * (1 mol Al/26.98 g Al) * (3 mol H₂/2 mol Al) = 0.0556x mol H₂.

Step 3

All that's left to do is multiply! Since we form 0.00556x moles of H₂, and each mole of gas fills 22.4 L at STP, 0.00556x*22.4 = 1.2454x L of H₂.

You're done! If you have any more questions, especially about the stoichiometry, let me know. Good luck!