Final answer:
To find the number of nickel atoms in a coin, first find the mass of nickel in the coin, convert that to moles using nickel's atomic mass, and then multiply the moles by Avogadro's number. The answer is 2.05 x 10²² nickel atoms.
Step-by-step explanation:
To calculate the number of nickel atoms in a coin with a mass of 10.0 g and 20% nickel by mass, you can use the following steps:
- Determine the mass of nickel in the coin by calculating 20% of 10.0 g, which equals 2.0 g.
- Convert grams of nickel to moles using the atomic mass of nickel (58.7 g/mol). This is done by dividing the mass of nickel by the atomic mass:
2.0 g ÷ 58.7 g/mol = 0.0341 mol
- Calculate the number of atoms by multiplying the number of moles by Avogadro's number (6.022 × 10²³ atoms/mol):
0.0341 mol × 6.022 × 10²³ atoms/mol = 2.05 × 10²² atoms
Therefore, the number of nickel atoms in the coin is 2.05 × 10²², which corresponds to answer choice a. 2.05 x 10²².