Question

Stainless steel is an alloy of iron containing 5 percent nickel and 0.175 percent chromium. How many atoms of nickel are present in a 84 g sample of this alloy?
Answer in units of atoms

Answer 1

First you need to work out what mass of 84g of stainless steel is nickel, and because there's 5% you can simply divide by 20, giving 4.2g

Answer 2

First you need to work out what mass of 84g of stainless steel is nickel, and because there's 5% you can simply divide by 20, giving 4.2g

For this you can use the equation $Moles= \frac{Mass}{Mr}$

The mass, as was worked out previously, is 4.2g
The Mr, which is found on the periodic table, is 28

Moles = $\frac{4.2}{28}$ = 0.15mol

1mol = 6.023 x $10^{23}$ atoms

So, 0.15mol = 0.15 x 6.023 x $10^{23}$ = 9.0345 x $10^{22}$ atoms