Question

How many grams of chromium are needed to react with an excess of `CuSO_4` to produce 16.2 g Cu?

Answer 1

its `8.775g`

Explanation:

Write down the equation for this reaction and balance it

`3CuSO_4 + 2Cr = 3Cu +Cr_2(SO_4)_3`
Calculate the amount of moles of copper. We have `16g`, and its molar mass is `64g`:

`16/64 = 0.25`

And thus the mole for chromium will be `0.17`

As the ratio suggests `2:3`

Thus `(0.25*2)/ 3 = 0.17`

Use this mole and substitute in the equation `"moles"="mass"/"molar mass"` to calculate the mass which is `0.17 * 52= 8.775g`