Question

Francium-223 has a half life of 21.80min. a. How many nuclei are initially in a 25mg sample of francium?

Answer 1

There are $6.75\times 10^{19}$ nuclei in 25 mg of Francium

Explanation:

To find : Number of nucei present in 25 mg or 0.025 g of Francium

Molar mass of Francium = 223 g/mol

According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number  of particles.

To calculate the moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=\frac{0.025g}{223g/mol}=0.00011moles$

1 mole contains = $6.023\times 10^{23}$ nuclei

Thus 0.00011 mole contains = $\frac{6.023\times 10^{23}}{1}\times 0.00011=6.75\times 10^{19}$ nuclei

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