A sample of crushed rock is found to have 4.81 x10^21 atoms of gold, how many moles of gold are present in this sample? a) 7.99 x 10^-3 moles
b) 1.57 x 10^-1 moles
c) 1.25 x 10^3 moles
d) 2.47 x 10^5 moles

0.8 moles

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

\begin{gathered}n = \frac{N}{L} \\\end{gathered}

n=

L

N

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

We have

\begin{gathered}n = \frac{4.81 \times {10}^{23} }{6.02 \times {10}^{23} } = \frac{4.81}{6.02} \\ = 0.799003...\end{gathered}

n=

6.02×10

23

4.81×10

23

=

6.02

4.81

=0.799003...

We have the final answer as

0.8 moles

Hope this helps you

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6.4 cm (max) - 25 cm (min)