A pure copper cube has an edge length of 2.02 cm .

How many copper atoms does it contain? (volume of a cube = (edge length)3; density of copper = 8.96 g/cm3)

N =___ Cu atoms

The number of copper atoms in the pure copper cube is 7×10²³ atoms

We'll begin by calculating the volume of the copper. This can be obtained as follow:

Edge length (L) = 2.02 cm

V = L³

V = 2.02³

Volume = 8.242408 cm³

Density = 8.96 g/cm³

Mass = Density × Volume

Mass = 8.96 × 8.242408

From Avogadro's hypothesis,

1 mole of Cu = 6.02×10²³ atoms

Recall:

1 mole of Cu = 63.5 g

Thus,

63.5 g of Cu = 6.02×10²³ atoms

Therefore,

73.85 g of Cu =

Therefore, the number of copper atoms in the cube is 7×10²³ atoms

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6.9988 x 10²³

Explanation:

We begin by finding the volume of the cube;

L * W * H

2.02 * 2.02 * 2.02

= 8.242408 cm3

If the density of copper = 8.96 g/cm3, the whole cube weighs;

8.242408 cm3 * 8.96

= 73. 852 g

The molar mass of a Copper is 63.5460 g/mol.  The number Copper moles in the cube is;

73.852 / 63.5460

= 1.1622 moles

Remember the Avogadro number that states that there are 6.022×10^23 particles  per mol. Therefore the number of Copper atoms in the cube is;

1.1622 * 6.022×10^23

= 6.9988 x 10²³

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

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