Question

How many `Mg^(2+)` ions are present in 3.00 moles of `MgCl_2`?

Answer 1

`1.81" x "10^24 Mg^(2+) "ions"`

Explanation:

Step 1:
From the formula `MgCl_2`, we know that it's made from 1 `Mg^(2+)` and 2 `Cl^-` ions

• In 1 mol of `MgCl_2`, there's 1 mol of `Mg^(2+)`

We can use this relationship to calculate the moles of `Mg^(2+) "ions"` from the given 3.00 moles of `MgCl_2`.

Step 2:
Once we find the moles of `Mg^(2+)`, we can find the number of `Mg^(2+) "ions"` using Avogadro's number.

• 1 mol `Mg^(2+)` has `6.022` x `10^23` `Mg^(2+) "ions"`

Combining the 2 steps calculations:
`Mg^(2+)"ions"="3.00 mols " MgCl_2 xx ("1 mol " Mg^(2+))/("1 mol " MgCl_2)xx(6.022 " x " 10^23 Mg^(2+) ions)/("1 mol " Mg^(2+))=1.81" x "10^24 Mg^(2+) "ions"`