Question

1. Calculate the number of molecules in the following compunds:
a) 16g of H2CO3 b) 20g of HNO3 c) 30g of C6H12O6

2. Calculate the number of ions in the following compounds:
a) 10g of AlCl3 b) 30g of BaCl2 c) 58g of H2SO4 (aq)

Answer 1

1) a) 1.81  × 10²³ molecules (b) 1.93  × 10²³ molecules (c) 0.66× 10²³ molecules

2) a) 0.45× 10²³ions  (b) 0.84× 10²³ions (c) 3.6 × 10²³ions

Explanation:

1) Number of molecules:

The given problem will solve by using Avogadro number.

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.

The number 6.022 × 10²³ is called Avogadro number.

a) 16g of H₂CO₃

Number of moles = mass/ molar mass

Number of moles = 16 g/ 62.03 g/mol

Number of moles = 0.3 mol

1 mol = 6.022 × 10²³ molecules

0.3 mol ×  6.022 × 10²³ molecules /1 mol

1.81  × 10²³ molecules

b) 20g of HNO₃

Number of moles = mass/ molar mass

Number of moles = 20 g/ 63.01 g/mol

Number of moles = 0.32 mol

1 mol = 6.022 × 10²³ molecules

0.32 mol ×  6.022 × 10²³ molecules /1 mol

1.93  × 10²³ molecules

c) 30g of C₆H₁₂O₆

Number of moles = mass/ molar mass

Number of moles = 20 g/ 180.156 g/mol

Number of moles = 0.11 mol

1 mol = 6.022 × 10²³ molecules

0.11 mol ×  6.022 × 10²³ molecules /1 mol

0.66× 10²³ molecules

2. Calculate the number of ions in the following compounds:

a) 10g of AlCl₃

Number of moles = mass/ molar mass

Number of moles = 10g/ 133.34 g/mol

Number of moles = 0.075 mol

1 mol = 6.022 × 10²³ ions

0.075 mol ×  6.022 × 10²³ ions/1 mol

0.45× 10²³ions

b) 30g of BaCl₂

Number of moles = mass/ molar mass

Number of moles = 30g/ 208.23 g/mol

Number of moles = 0.14 mol

1 mol = 6.022 × 10²³ ions

0.14 mol ×  6.022 × 10²³ ions/1 mol

0.84× 10²³ions

c) 58 g of H2SO4

Number of moles = mass/ molar mass

Number of moles = 58g/ 98.079 g/mol

Number of moles = 0.59 mol

1 mol = 6.022 × 10²³ ions

0.59 mol ×  6.022 × 10²³ ions/1 mol

3.6 × 10²³ions