Question

If a penny is made of 3.11 grams of copper, how many atoms of copper are in the penny

Answer 1

There are 2.94 x 10²²atoms in 3.11 grams of copper penny.

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We first find the number of moles contained in 3.11 grams of copper

Number of moles =Mass/ Molar mass

Molar mass of copper is 63.546g/mol

Number of moles = 3.11 g/63.546g/mol =0.0489moles

But 1 mole of Cu= 6.022x10²³(Avogadro's number ) atoms of Cu

Therefore 0.0489 moles of Cu will give 0.0489 x 6.02x10²³ atoms Cu =2.94 x 10²²atoms

Answer 2

2.94x10²² atoms of Cu

Step-by-step explanation:

We must work with NA to solve this, where NA is the number of Avogadro, number of particles of 1 mol of anything.

Molar mass Cu = 63.55 g/mol

Mass / Molar mass = Mol → 3.11 g / 63.55 g/m = 0.0489 moles

1 mol of Cu has 6.02x10²³ atoms of Cu

0.0489 moles of Cu, will have (0.0489 .NA)/ 1 = 2.94x10²² atoms of Cu