Question

Find the number of atoms in 0.470 g of Ca (20Ca40 and 1 amu = 1.66 X 10-24 g) (You can also use the Avogadro’s number 6.022 X 1023).

Answer 1

In 0.470 grams of Calcium, there are 7.05 * 10^21 Ca atoms

Step-by-step explanation:

Step 1: Data given

We have 0.470 grams of Calcium (Ca)

Calcium has a molar mass of 40.08 amu

Avogadro's number, is the number of units in one mole of any substance and is equal to 6.022 * 10^23

Step 2: Calculate number of moles of Calcum

Number of moles of calcium = mass of Calcium / Molar mass of calcium

Number of moles of calcium = 0.470 grams / 40.08 g/mole = 0.0117 moles

Step 3 : Calculate number of atoms

Since the Avogadro's number says that there are 6.022 *10^23 atoms in 1 mole

This means that in 0.0117 moles of Calcium, we have 0.0117 * 6.022 *10^23 = 7.05 * 10^21 atoms

In 0.470 grams of Calcium, there are 7.05 * 10^21 Ca atoms