Question

A student is given 1.525 g of pure CuO. To recover the Cu present in the compound, the dark powdery solid was dissolved in 15.0 mL of 6 M HCl, the solution diluted with 50.0 mL of water, and 0.50 g of Mg was added. Was this enough Mg to displace all the ions from the solution

Answer 1

The amount of Mg was enough

Step-by-step explanation:

In this case, we have to start with the reaction between
`Mg` and
`CuO`, so:

`CuO~+~Mg~->~MgO~+~Cu`

If we check the reaction is already balanced. Now, we can do some stoichiometry to calculate the amount of Mg. The first step is the number of moles of
`CuO`. To this we have to calculate the molar mass of
`CuO` first, so:

Cu: 63.55 g/mol and O: 16 g/mol. So, (63.55+16)= 79.55 g/mol.

Now, we can calculate the moles:

`1.525~g~CuO(1~mol~CuO)/(79.55~g~CuO)=0.0192~mol~CuO`

The molar ratio between
`Mg` and
`CuO` is 1:1, so:

`0.0192~mol~CuO=0.0192~mol~Mg`.

Now we can calculate the mass of Mg if we know the atomic mass of Mg (24.305 g/mol). So:

`0.0192~mol~Mg(24.305~g~Mg)/(1~mol~Mg)=0.466~g~Mg`

With this in mind, the student added enough Mg to recover all the Cu.

Note: The HCl doesn't take a role in the reaction. The function of HCl is to dissolve the
`CuO`.

I hope it helps!