Question

Calculate the number of nickel atoms in a 5-cent coin of mass 0.942g if it was made of an alloy consisting of 75% copper and 25% nickel.

Answer 1

2.41x10²¹ atoms

Step-by-step explanation:

First we calculate the mass of nickel in the coin, using the given mass and percent composition:

• 0.942 g * 25/100 = 0.2355 g Ni

Then we convert 0.2355 grams of nickel to moles, using its molar mass:

• 0.2355 g Ni ÷ 58.69 g/mol = 0.004 mol

Finally we convert moles into number of atoms, using Avogadro's number:

• 0.004 mol * 6.023x10²³ atoms/mol = 2.41x10²¹ atoms