[_rob]

The question asks to calculate the percent (does not specify whether it wants % by mass or % by moles which i find ambiguous) of Zinc in a Zinc-Copper alloy with mass 6.1g, when reacting with excess HCL. The volume of Hydrogen gas produced is 1.26mL at 22C and pressure 728mmHg.

I have a rough idea of the answer, but seems like a very very small percent to be a real alloy, so it's making me question it.

I would firstly go about calculating the moles of H2 produced using Pv=nRT, which i get to be roughly 5x10-5 moles which makes sense.

Secondly I would say that 1 mole of Zinc reacts to make one mole of H2 gas

Zn + 2HCL ----->ZnCl2 + H2

so moles of Zinc reacted = roughly 5 x10-5

I would then use mass = moles x MM to get the mass of Zinc as 3.26x10-3g, which is obvously going to be a very small percentage of Zinc in a 6.1g alloy sample!

Am i doing something stupid or is this just a very low % Zinc alloy?!


Thank you for any help guys...

Rob

[Borek]

You can be sure it asks for mass % w/w.

3.26e-3g Zn is correct for a given data. Low, but correct.

[_rob]

Thank you very much