Respuesta :
The question requires us to calculate the number of atoms in 25.75 g of Hg, 0.0740 g of Mg and 160 g of Br.
To calculate the number of atoms in a sample, given its mass, we need to use the Avogadro's number, which defines the number of particles (atoms, molecules, ions etc.) in 1 mol of any substance as 6.02 x 10^23 particles.
Using the Avogadro's number, we can write:
1 mol of substance (in mol) = atomic mass or molar mass (in g) --------------- 6.02 x 10^23 particles
mass of a sample (in g) ----------------------------- x
(where x is the value we want to calculate - the number of particles).
Solving for x, we'll have:
[tex]x=\frac{(mass\text{ of a sample, g)}\times(6.02\times10^{23}\text{ particles)}}{(\text{atomic or molar mass of substance, g)}}[/tex]Therefore, to calculate the number of atoms in the samples given by the question, we need the atomic mass of the elements (Hg, Mg and Br), the mass of the sample (given by the question) and the Avogadro number (6.02 x 10^23 particles/mol).
Next, we'll calculate the number of atoms for each sample using the equation above:
• For 25.75 g of Hg:
The atomic mass of Hg is 200.59 u. We can apply the equation as it follows:
[tex]x=\frac{(25.75g\text{)}\times(6.02\times10^{23}\text{ atoms)}}{(\text{200.59 g)}}=7.728\times10^{22}\text{ atoms}[/tex]Therefore, there are 7.728 x 10^22 atoms in 25.75 g of Hg.
For 0.0740 g of Mg:
The atomic mass of Mg is 24.305 u. We can calculate the amount of atoms as it follows:
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