Which of the following samples contains the greatest number of atoms.
1) 100g of Pb
2) 5g of He
3) 2.0 moles of Ar
4) 0.1 mole of Fe
5) 20 million O2 molecules
not sure how to go about this and would appreciate any insight
You know one (1) mole of anything contains 6.02E23 atoms.Therefore, calculate moles of each of the substances listed. The larges mols OF ATOMS wins. moles = grams/atomic mass. For Pb that is
100 g/207.whatever = ?
Be careful with O2. That is a MOLECULE so after you find the moles of the MOLECULE O2 you must multiply by 2 to get the number of ATOMS.
good advice on the O2, but since a million is so much less than 6.02E23, you can ignore it from the get-go.
The others are in grams or moles, so they are at least in the same ball park.
@oobleck-----but I always do things the hard way. Keeps me consistent.
To determine which sample contains the greatest number of atoms, we need to compare the number of atoms in each sample.
To calculate the number of atoms in a given amount of substance, we can use Avogadro's number, which is approximately 6.022 x 10^23 atoms/mol. This value represents the number of atoms in one mole of any substance.
Let's go through each choice step by step:
1) 100g of Pb:
To determine the number of moles of Pb in 100g, we need to divide the mass by the molar mass of Pb. The molar mass of Pb is approximately 207.2 g/mol.
Number of moles = mass (g) / molar mass (g/mol)
Number of moles = 100g / 207.2 g/mol ≈ 0.482 mol
Since there are approximately 6.022 x 10^23 atoms in one mole, we can calculate the number of atoms in 0.482 mol:
Number of atoms = Number of moles x Avogadro's number
Number of atoms = 0.482 mol x 6.022 x 10^23 atoms/mol ≈ 2.901 x 10^23 atoms
2) 5g of He:
To determine the number of moles of He in 5g, we need to divide the mass by the molar mass of He. The molar mass of He is approximately 4 g/mol.
Number of moles = mass (g) / molar mass (g/mol)
Number of moles = 5g / 4 g/mol = 1.25 mol
Number of atoms = Number of moles x Avogadro's number
Number of atoms = 1.25 mol x 6.022 x 10^23 atoms/mol ≈ 7.528 x 10^23 atoms
3) 2.0 moles of Ar:
As 2.0 moles of Ar is already given, we can directly use the Avogadro's number to calculate the number of atoms:
Number of atoms = Number of moles of Ar x Avogadro's number
Number of atoms = 2.0 mol x 6.022 x 10^23 atoms/mol = 1.2044 x 10^24 atoms
4) 0.1 mole of Fe:
Number of atoms = Number of moles of Fe x Avogadro's number
Number of atoms = 0.1 mol x 6.022 x 10^23 atoms/mol = 6.022 x 10^22 atoms
5) 20 million O2 molecules:
To calculate the number of atoms in 20 million O2 molecules, we need to consider that each O2 molecule contains 2 oxygen atoms.
Number of atoms = Number of O2 molecules x 2 atoms per molecule
Number of atoms = 20,000,000 molecules x 2 atoms/molecule = 40,000,000 atoms
Now, comparing the number of atoms in each sample:
1) 2.901 x 10^23 atoms
2) 7.528 x 10^23 atoms
3) 1.2044 x 10^24 atoms
4) 6.022 x 10^22 atoms
5) 40,000,000 atoms
Hence, sample 3 (2.0 moles of Ar) contains the greatest number of atoms with approximately 1.2044 x 10^24 atoms.