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If 195g Pt ----- contains -------- 6,02×10²³
so  x         ----- contains -------- 4,92×10²¹

\(x=\frac{4,92*10^{21}*195g}{6,02*10^{23}}\approx 195,4*10^{-2}g=1,954g\)

Answer:

1.593 grams is the mass of \(4.92\times 10^{21}\) platinum atoms.

Explanation:

\(N=n\times N_A\)

\(m=n\times M\)

Where:

N = Number of particles / atoms/ molecules

n = Number of moles

m = mass of sample

M = Atomic mass

\(N_A=6.022\times 10^{23} mol^{-1}\) = Avogadro's number

We have:

Atoms of platinum  = N = \(4.92 \times 10^{21}\)

Moles of platinum = n =?

\(n=\frac{N}{N_A}=\frac{4.92\times 10^{21}}{6.022\times 10^{23} mol^{-1}}\)

n = 0.008170 moles

Mass of N platinum atoms = m

Atomic mass of the platinum atom = m = 195 g/mol

\(m=0.008170 mol\times 195 g/mol=1.593 g\)

1.593 grams is the mass of \(4.92\times 10^{21}\) platinum atoms.