Gas law problem?

[Swenis]

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Hey guys and gals! I was wondering if anyone of you could help me with this gas law problem?

An alloy of aluminum and magnesium is treated with a sodium hydroxide solution; only the aluminum reacts:
2 Al(s) + 2 NaOH(aq)+ 6 H2O(l) ------> 2 NaAl(OH)4(aq) + 3 H2(g)

1.118 g of the alloy forms 1.453 L of hydrogen collected over water at 25oC and 700. mm Hg. What is the % Al in the alloy?

This sucker is killing me. All of the other probs have been cake, but I'm not comprehending this one. Thank you guys so much! 👍

 

[TMVegas]

Hey guys and gals! I was wondering if anyone of you could help me with this gas law problem?

An alloy of aluminum and magnesium is treated with a sodium hydroxide solution; only the aluminum reacts:
2 Al(s) + 2 NaOH(aq)+ 6 H2O(l) ------> 2 NaAl(OH)4(aq) + 3 H2(g)

1.118 g of the alloy forms 1.453 L of hydrogen collected over water at 25oC and 700. mm Hg. What is the % Al in the alloy?

This sucker is killing me. All of the other probs have been cake, but I'm not comprehending this one. Thank you guys so much! 👍

I could be completely wrong (its been 2 yrs since gen chem) but here is how I think you solve it:


convert the L of H2, temp and pressure to moles of H2 using PV=nRT

take the moles of H2 from this equation and convert it to g of Al using stoichiometery

divide the grams used by the grams of the alloy you started with and multiply by 100%

hope this helps and I hope it is right

 

[Swenis]

Arrg I'm an idiot lol. I originally did the problem exactly as you described it, but could not get the right answer. It turned out that I didn't convert mm Hg to atm haha. Thanks!