* Atoms have different masses: Each element has a different atomic mass. For example, a carbon atom is much lighter than a gold atom.
* Mass is a measure of the amount of matter: 68.0 kg represents a specific amount of matter, but it doesn't tell us what kind of matter.
To calculate the number of atoms, you need:
1. The chemical formula of the substance: This tells you what elements are present and in what ratio.
2. Avogadro's number: This constant relates the number of atoms in a mole (6.022 x 10^23 atoms/mol).
Here's how you would do it:
1. Calculate the number of moles: Divide the mass (68.0 kg) by the molar mass of the substance.
2. Multiply by Avogadro's number: This gives you the number of atoms in that many moles.
Example:
Let's say you want to find the number of atoms in 68.0 kg of pure gold (Au).
1. Molar mass of gold (Au): 196.97 g/mol
2. Convert kg to g: 68.0 kg * 1000 g/kg = 68000 g
3. Calculate moles: 68000 g / 196.97 g/mol = 345.2 mol
4. Calculate atoms: 345.2 mol * 6.022 x 10^23 atoms/mol = 2.08 x 10^26 atoms
In summary, you need to know the specific substance to determine the number of atoms in a given mass.
