# What is the mass of 4*10^21 platinum atoms?

May 16, 2016

The mass of $4 \times {10}^{21}$ atoms Pt is" ~~ 1 g Pt.

#### Explanation:

There are two equalities required to answer this question.

$6.022 \times {10}^{23} \text{atoms}$$=$$1 \text{mol atoms}$

$1 \text{mol Pt}$$=$$195.084 \text{g Pt}$ (molar mass of Pt)

Then carry out the following operations.

Divide the given number of atoms of Pt by the number of atoms of Pt in a mole. Then multiply by the molar mass of Pt.

$4 \times {10}^{21} \cancel{\text{atoms Pt"xx(1cancel"mol Pt")/(6.022xx10^23cancel"atoms Pt")xx(195.084"g Pt")/(1cancel"mol Pt")="1 g Pt}}$ (rounded to one significant figure)