<u>Answer:</u>
<u>For A:</u> The number of arsenic atoms are ![3.4\times 10^{21}](https://tex.z-dn.net/?f=3.4%5Ctimes%2010%5E%7B21%7D)
<u>For B:</u> The percent composition of mercury, thallium and chromium in their complexes are 61.76 %, 62.2 % and 29.51 % respectively.
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
![\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}](https://tex.z-dn.net/?f=%5Ctext%7BNumber%20of%20moles%7D%3D%5Cfrac%7B%5Ctext%7BGiven%20mass%7D%7D%7B%5Ctext%7BMolar%20mass%7D%7D)
Given mass of dimercaprol = 696 mg = 0.696 g (Conversion factor: 1 g = 1000 mg)
Molar mass of dimercaprol = 124.21 g/mol
Putting values in above equation, we get:
![\text{Moles of dimercaprol}=\frac{0.696g}{124.21g/mol}=0.0056mol](https://tex.z-dn.net/?f=%5Ctext%7BMoles%20of%20dimercaprol%7D%3D%5Cfrac%7B0.696g%7D%7B124.21g%2Fmol%7D%3D0.0056mol)
According to mole concept:
1 mole of a compound contains
number of molecules.
So, 0.0056 moles of dimercaprol will contain
number of molecules.
As, 1 molecule of dimercaprol binds with 1 atom of Arsenic
So,
number of dimercaprol molecules will bind with =
number of arsenic atoms
Hence, the number of arsenic atoms are ![3.4\times 10^{21}](https://tex.z-dn.net/?f=3.4%5Ctimes%2010%5E%7B21%7D)
We know that:
Molar mass of dimercaprol = 124.21 g/mol
Molar mass of mercury = 200.59 g/mol
Molar mass of thallium = 204.38 g/mol
Molar mass of chromium = 51.99 g/mol
Also, 1 molecule of dimercaprol binds with 1 metal atom.
To calculate the percentage composition of metal in a complex, we use the equation:
......(1)
Mass of Hg-complex = (200.59 + 124.21) = 324.8 g
Mass of mercury = 200.59 g
Putting values in equation 1, we get:
![\%\text{ composition of mercury}=\frac{200.59g}{324.8g}\times 100=61.76\%](https://tex.z-dn.net/?f=%5C%25%5Ctext%7B%20composition%20of%20mercury%7D%3D%5Cfrac%7B200.59g%7D%7B324.8g%7D%5Ctimes%20100%3D61.76%5C%25)
Mass of Tl-complex = (204.38 + 124.21) = 328.59 g
Mass of thallium = 204.38 g
Putting values in equation 1, we get:
![\%\text{ composition of thallium}=\frac{204.38g}{328.59g}\times 100=62.2\%](https://tex.z-dn.net/?f=%5C%25%5Ctext%7B%20composition%20of%20thallium%7D%3D%5Cfrac%7B204.38g%7D%7B328.59g%7D%5Ctimes%20100%3D62.2%5C%25)
Mass of Cr-complex = (51.99 + 124.21) = 176.2 g
Mass of chromium = 51.99 g
Putting values in equation 1, we get:
![\%\text{ composition of chromium}=\frac{51.99g}{176.2g}\times 100=29.51\%](https://tex.z-dn.net/?f=%5C%25%5Ctext%7B%20composition%20of%20chromium%7D%3D%5Cfrac%7B51.99g%7D%7B176.2g%7D%5Ctimes%20100%3D29.51%5C%25)
Hence, the percent composition of mercury, thallium and chromium in their complexes are 61.76 %, 62.2 % and 29.51 % respectively.