Select the correct mass for each of the samples described below.

Explanation:

Given data:

Number of molecules of H₂O = 3.01 × 10²³

Mass of H₂O = ?

Solution:

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.

For example,

1 mole = 6.022 × 10²³ molecules

3.01 × 10²³ molecules × 1 mol / 6.022 × 10²³ molecules

0.5 moles of water

Mass of water:

Mass = number of moles × molar mass

Mass = 0.5 mol  × 18 g/mol

Mass = 9 g

2)

Number of formula units of CaBr₂ = 8.32 × 10²⁰

Mass of CaBr₂ = ?

Solution:

8.32 × 10²⁰ formula units × 1 mol / 6.022 × 10²³ formula units

1.4×10⁻³ moles of CaBr₂

Mass of CaBr₂:

Mass = number of moles × molar mass

Mass = 1.4×10⁻³ mol × 199.89 g/mol

Mass = 279.85×10⁻³ g

3)

Number of molecules of XeF₆ = 1.93 × 10²⁶

Mass of XeF₆ = ?

Solution:

1.93 × 10²⁶ molecules × 1 mol / 6.022 × 10²³ molecules

0.32 × 10³ mol

Mass of XeF₆:

Mass = number of moles × molar mass

Mass = 0.32 × 10³ mol × 245.28 g/mol

Mass = 78.5 × 10³ g