Calculate the following quantities. (See the periodic table.)
(a) mass, in grams, of 2.54 10-2 mol of CdS
g
(b) number of moles of NH4Cl in 90.0 g of this substance
mol
(c) number of molecules in 5.081 10-2 mol C6H6
molecules
(d) number of O atoms in 4.72 10-3 mol Al(NO3)3
You need to remember two formula for this. For mass, g, mols, it is
mols = grams/molar mass. That will do a and b.
For # molecules, remember that 1 mol of anything contains 6.02E23 of those anythings. That will do c and d.
To calculate the quantities, you will need to use the molar mass and Avogadro's number.
(a) To find the mass of 2.54 x 10^-2 mol of CdS:
- First, you need to find the molar mass of CdS by looking up the atomic masses of Cd and S on the periodic table.
- The atomic mass of Cd is 112.41 g/mol and the atomic mass of S is 32.07 g/mol.
- Now, you can calculate the molar mass of CdS by adding the atomic masses together: 112.41 g/mol + 32.07 g/mol = 144.48 g/mol
- Finally, to find the mass of 2.54 x 10^-2 mol of CdS, you multiply the molar mass by the number of moles: 144.48 g/mol x 2.54 x 10^-2 mol = 3.67 g
(b) To find the number of moles of NH4Cl in 90.0 g of the substance:
- First, you need to find the molar mass of NH4Cl by looking up the atomic masses of N, H, and Cl on the periodic table.
- The atomic mass of N is 14.01 g/mol, the atomic mass of H is 1.01 g/mol, and the atomic mass of Cl is 35.45 g/mol.
- Now, you can calculate the molar mass of NH4Cl by adding the atomic masses together: 14.01 g/mol + 1.01 g/mol + (4 x 1.01 g/mol) + 35.45 g/mol = 53.49 g/mol
- Finally, to find the number of moles of NH4Cl in 90.0 g, you divide the given mass by the molar mass: 90.0 g / 53.49 g/mol = 1.68 mol
(c) To find the number of molecules in 5.081 x 10^-2 mol of C6H6:
- Avogadro's number tells us that there are 6.022 x 10^23 molecules in 1 mole of any substance.
- So, to find the number of molecules in 5.081 x 10^-2 mol of C6H6, you multiply the given number of moles by Avogadro's number: 5.081 x 10^-2 mol x 6.022 x 10^23 molecules/mol = 3.06 x 10^22 molecules
(d) To find the number of O atoms in 4.72 x 10^-3 mol of Al(NO3)3:
- First, calculate the molar mass of Al(NO3)3.
- The atomic mass of Al is 26.98 g/mol, the atomic mass of N is 14.01 g/mol, and the atomic mass of O is 16.00 g/mol.
- Now, you can calculate the molar mass of Al(NO3)3 by adding the atomic masses together: 26.98 g/mol + (3 x 14.01 g/mol) + (3 x 16.00 g/mol) = 213.01 g/mol
- Finally, to find the number of O atoms in 4.72 x 10^-3 mol of Al(NO3)3, you multiply the number of moles by the number of O atoms in each molecule (which is 3): 4.72 x 10^-3 mol x 3 = 1.416 x 10^-2 moles.