1. How many moles are in 5.6 x 10 23 atoms of Na?

2. How many moles are in 25.6 atoms of Cu?

3. How many atoms are in 56.5 moles of Li?

4. How many atoms are in 25.5 moles of oxygen? (O2)

5. How many grams of magnesium are in 225.6 moles of magnesium?

(Show Work)

0.93moles of Na

4.25 x 10⁻²³ moles of Cu

3.4 x 10²⁵atoms of Li

1.53 x 10²⁵ atoms of oxygen

5.48kg

Explanation:

1. How many moles are in 5.6 x 10 23 atoms of Na?

Problem 1:

Given parameters:

Number of atoms of Na = 5.6 x 10²³ atoms

Unknown:

Number of moles of Na = ?

Solution:

To solve this problem, we are going to adopt the mole concept. A mole of a substance is defined as the amount of a substance that contains the avogadro's number of particles.

     Avogadro's number of particles = 6.02 x 10²³

Particles = atoms, molecules, formula units, protons, neutrons, electrons

       6.02 x 10²³ atoms of Na  = 1 mole

       5.6 x 10²³ atoms of Na =    =  0.93moles

2. How many moles are in 25.6 atoms of Cu?

Given parameters:

Number of atoms of Cu = 25.6 atoms

Unknown;

Number of moles  = ?

Solution:

The mole concept also works in this case since we know that;

         1 mole of substance  =  6.02 x 10²³ atoms

          x mole of Cu =   25.6 atoms;

      Number of moles of Cu  =     = 4.25 x 10⁻²³ moles

3. How many atoms are in 56.5 moles of Li?

Given parameters:

Number of moles of Li = 56.5 moles

Unknown;

Number of atoms of Li = ?

Solution:

Since we have been given the number of moles, we can find the amount of atoms contained in this mole of Lithium.

We must understand that a mole of any substance contains the avogadro's number of particles.

        1 mole of a substance   =   6.02 x 10²³ atoms

          56.5 mole of Li  = 56.5 moles x  6.02 x 10²³ atoms  = 3.4 x 10²⁵atoms

4. How many atoms are in 25.5 moles of oxygen? (O2)

Given parameters:

Number of moles given = 25.5 moles of Oxygen

Unknown:

Number of atoms = ?

Solution;

  To find the number of atoms in a substance;

          Number of atoms  = number of moles x 6.02 x 10²³

This is because 1 mole of any substance contains 6.02 x 10²³ particles.

Substitute for the number of moles in the equation;

         Number of atoms  = 25.5 x 6.02 x 10²³  = 1.53 x 10²⁵ atoms of oxygen

5. How many grams of magnesium are in 225.6 moles of magnesium?

Given parameters:

Number of moles of Mg = 225.6moles

Unknown:

Mass of Mg = ?

Solution:

We are still going to use the mole concept to solve this problem. A mole of substance can also be related to the mass any element or compound;

          Number of moles  =

        Mass  = number of moles x molar mass

From the periodic table, the molar mass of Mg  = 24.3g/mol

    Mass  = 225.6 x 24.3  = 5482.08g = 5.48kg

the answer to this question is 3.