Question

How many molecules (or formula units) are in each sample?

75.52 g CCl4

91.69 kg NaHCO3

124.34 g C4H10

2.06×10⁴ g Na3PO4

Answer 1

Answer – We are given the mass of compounds and need to calculate molecules, so first we need to calculate the moles of each then fomr mole to molecules as follow –

1)Mass of CCl₄ =75.52 g , molar mass of CCl₄= 153.8 g/mol

Moles of CCl₄ =75.52 g / 153.8 g/mol

                        = 0.491 moles

We know

1 mole = 6.023*10²³ molecules

So, 0.491 moles = ?

= 2.96*10²³ molecules of CCl₄

2) Mass of NaHCO₃ = 91.69 kg = 91690 g

molar mass of NaHCO₃ = 84.00 g/mol

Moles of NaHCO₃ =91690 g / 84.00 g/mol

                        = 1091.5 moles

We know

1 mole = 6.023*10²³ molecules

So, 1091.5 moles = ?

= 6.57*10²⁶ molecules of NaHCO₃

3) Mass of C₄H₁₀ = 124.34 g

molar mass of C₄H₁₀ = 58.12 g/mol

Moles of C₄H₁₀= 124.34 g / 58.12 g/mol

                        = 2.14 moles

We know

1 mole = 6.023*10²³ molecules

So, 2.14 moles = ?

= 1.29*10²⁴ molecules of C₄H₁₀

4) Mass of Na₃PO₄ = 2.06*10⁴ g

molar mass of Na₃PO₄ = 163.94 g/mol

Moles of Na₃PO₄ = 2.06*10⁴ g / 163.94 g/mol

                            = 125.6 moles

We know

1 mole = 6.023*10²³ molecules

So, 125.6 moles = ?

= 7.57*10²⁵ molecules of Na₃PO₄