[gotalbin]

Brass in an alloy of Cu and Zn. Even though the composition may vary, an alloy rich in Cu is a higher quality brass. A piece of 10 g of brass attacked by HCL (aq) releases 1.12 L of hydrogen gas at STP. What is the percent composition of Cu in this brass piece and how many mL of a 6M solution is used to dissolve this piece.

For the first part I suppose the reaction equation would be:

Cu + HCl -------------->  CuCl + H₂
Zn + HCl --------------> ZnCl + H₂

Then we use the gas law equation to find the moles of hydrogen gas and then we set up and solve a system of equations.

[Borek]

Is copper reacting with HCl?

[Bo_2Q]

 67.5% Cu 
Cu can't react with HCl
 But 2Cu + 4HCl + O2 ---> 2CuCl2 + 2H2O 

[AWK]

Both reaction are wrong

Cu + HCl -------------->  CuCl + H2
Zn + HCl --------------> ZnCl + H2

Moreover copper does not react with HCl in this conditions (reductive, since H2 is evolved during reaction of HCl with zinc).