Calculate the number of moles and atoms.

A)64 gm of O2
B)58.9 gm of CI
C)90.5gm of (HN4)2SO4
D)243gm of Mg2

moles = grams/molar mass

1 mol of anything contains 6.022E23 atoms.

To calculate the number of moles and atoms, you need to use the concept of chemical stoichiometry and Avogadro's number.

1. A) Calculating moles and atoms for 64 g of O2:
- Firstly, determine the molar mass of O2 (oxygen gas) using the periodic table.
- Molar mass of O = 16 g/mol
- Since O2 consists of two oxygen atoms, the molar mass of O2 is 2 * 16 g/mol = 32 g/mol
- Now, use the formula: moles = mass / molar mass
- Moles of O2 = 64 g / 32 g/mol = 2 mol
- To calculate the number of atoms, use Avogadro's number which states that there are 6.022 x 10^23 atoms in one mole of any substance.
- Number of atoms in 2 moles of O2 = 2 mol * (6.022 x 10^23 atoms/mol) = 1.2044 x 10^24 atoms

2. B) Calculating moles and atoms for 58.9 g of Cl:
- Find the molar mass of Cl (chlorine) from the periodic table.
- Molar mass of Cl = 35.45 g/mol (approximately)
- Apply the formula: moles = mass / molar mass
- Moles of Cl = 58.9 g / 35.45 g/mol = 1.66 mol (approximately)
- To calculate the number of atoms, multiply the moles by Avogadro's number.
- Number of atoms in 1.66 mol of Cl = 1.66 mol * (6.022 x 10^23 atoms/mol) = 9.9972 x 10^23 atoms (approximately)

3. C) Calculating moles and atoms for 90.5 g of (NH4)2SO4 (ammonium sulfate):
- Determine the molar mass of (NH4)2SO4 by adding up the atomic masses of each element in the compound.
- Molar mass of N = 14 g/mol
- Molar mass of H = 1 g/mol
- Molar mass of S = 32 g/mol
- Molar mass of O = 16 g/mol
- Multiply the atomic masses by their respective subscripts and sum them up:
(2 * 14 g/mol) + (8 * 1 g/mol) + 32 g/mol + (4 * 16 g/mol) = 132 g/mol
- Use the formula: moles = mass / molar mass
- Moles of (NH4)2SO4 = 90.5 g / 132 g/mol = 0.685 mol (approximately)
- To calculate the number of atoms, multiply the moles by Avogadro's number.
- Number of atoms in 0.685 mol of (NH4)2SO4 = 0.685 mol * (6.022 x 10^23 atoms/mol) = 4.1277 x 10^23 atoms (approximately)

4. D) Calculating moles and atoms for 243 g of Mg2:
- In the problem statement, the compound "Mg2" seems to be missing necessary information. Please provide the correct chemical formula or compound name so that I can assist you further with the calculation.