How many atoms are there in a 15.0-g sample of KBr?
To determine the number of atoms in a sample of KBr, we need to follow these steps:
Step 1: Find the molar mass of KBr
The molar mass of KBr can be calculated by summing the atomic masses of potassium (K) and bromine (Br).
The atomic mass of potassium (K) is 39.10 g/mol, and the atomic mass of bromine (Br) is 79.90 g/mol.
Molar mass of KBr = atomic mass of K + atomic mass of Br = 39.10 g/mol + 79.90 g/mol = 119.00 g/mol
Step 2: Convert the given mass to moles
We have a 15.0-g sample of KBr. To convert grams to moles, divide the mass by the molar mass.
Number of moles = mass of sample (g) / molar mass (g/mol)
Number of moles = 15.0 g / 119.00 g/mol = 0.1261 mol
Step 3: Use Avogadro's number to convert moles to atoms
Avogadro's number is 6.022 x 10^23 atoms/mol. Multiply the number of moles by Avogadro's number to find the number of atoms.
Number of atoms = number of moles x Avogadro's number
Number of atoms = 0.1261 mol x (6.022 x 10^23 atoms/mol) = 7.59 x 10^22 atoms
Therefore, there are approximately 7.59 x 10^22 atoms in a 15.0-g sample of KBr.