[Johulus]

By reaction between 25 g of heterogeneous aluminum, zinc and copper mixture and sodium hydroxide solution, 9.73 dm³ of hydrogen is released at STP conditions. By reaction between hydrocloric acid and 20 g of newly formed sample, 14.48 dm³ of hydrogen is released. Determine the mass of aluminum, zinc and copper in heterogeneous mixture given.

I don't really know even which reactions would take place here. That's the main problem. I apologize for translation which is probably not at high level but I did my best. Would appreciate your *delete me*

[Hunter2]

Aluminium and Zinc reacting either with NaOH or HCl.  With NaOH you get hydroxicomplex. So look up these complexes and you can develop the reaction equation. HCl also reacts with these metals and form hydrogen. Also here you have to develop the equation. You get four equations and you have two variables. It should be solvable. The copper will be in both cases not attacked.

[Johulus]

That's what I thought. But why copper won't react? Also, I'm not sure if it was clear but those are two different sequences first NaOH is added to the mixture, and then hydrochloric acid is added to what was left. At least that's how I figured it should be. So, aluminum reacts with NaOH and also zinc in two separate equations and then the products with hydrochloric acid? In addition, all three metals are less reactive than Na and can't replace it in NaOH? I don't understand what happens then and why? I've found some equations online but I don't know if that's what happens here.

[Hunter2]

Read the execise again. You have two samples. One is treated with NaOH the other one is treated with HCl. You get two different amount of  hydrogen gas.

Copper ist too noble. It will not react.

[Johulus]

To 25 g of initial heterogeneous mixture NaOH aqueous is added. Copper doesn't react with NaOH as earlier is said, but zinc and aluminum do react with NaOH. During the reaction 9.73 dm³ of hydrogen gas is released at STP conditions. Reactions should be:

Zn_(s) + 2NaOH_(aq) + 2H₂O_(l) Na₂Zn(OH)_4(s) + H_2(g)
and
2Al_(s)+2NaOH_(aq)+2H₂O_(l) 2NaAlO_2(s) + H_2(g)

I don't know if this is good or not. I've tried to consult the internet but I don't know. Then HCl_(aq) is added to what is left, and also hydrogen gas should be released at STP conditions; 14.48 dm³ of hydrogen.

[Hunter2]

No the first sample is treated-with NaOH, the second one  with HCl.

Not the same sample.

The reaction equation with Al is wrong. You will get [Al(OH)₄]^-