[OKubowski]

Hello everyone, it's nice to be posting here for the first time. Please let me know if I'm breaking any forum etiquette and I'll be sure to clean up my act.

I'm stuck on this problem:

Consider the following reaction.

Mg(s) + 2HCl(aq) --> MgCl₂(aq) + H₂O(l) + CO₂(g)

What minimum amount of 1.65 M HCl is necessary to produce 26.5 L of H₂ at STP?

I've worked this problem again and again, and I just can't seem to set it up correctly. Any help would be much appreciated.

[billnotgatez]

Mg(s) + 2HCl(aq) --> MgCl2(aq) + H2O(l) + CO2(g)

Is this a balanced equation?

[OKubowski]

Here is the solution:

26.5L H₂ x 1 mol H₂/22.4L H₂(g) x 2 mol HCl/1mol H₂ x 1L HCl(g)/1.65 mol HCl = 1.43L HCl

I actually derived this solution myself, but incorrectly reasoned that it must have been wrong. It didn't make sense to me that 1.43L of HCl could produce 26.5L of H₂ gas. When I see the 2:1 ratio of HCl to H₂ in the chemical equation, it's hard to see how so little HCL gas can produce so much H₂ gas. I might be able to figure it out when I'm feeling less burnt out, but I'd like to understand this. (Aiming for mastery here.)

[OKubowski]

I'm sorry, arrgghh, the original equation should have been:

Mg(s) + 2HCl(aq) MgCl₂(aq) + H₂(g)

[billnotgatez]

does a balanced equation help you understand the problem better