How many molecules are present in a drop of ethanol, c2h5oh, of mass 2.3*10^-2.3g? (na=6.0*10^23mol^-1)
explain why
a) 3.0*10^19
b) 3.0*10^20
c) 6.0*10^20
d) 6.0*10^26

3.0 × 10²⁰ molecules

Explanation:

Given data:

Mass of ethanol = 2.3 × 10⁻²°³ g

Number of molecules = ?

Solution:

Number of moles of ethanol:

Number of moles = mass/ molar mass

Number of moles = 2.3 × 10⁻²°³ g / 46.07 g/mol

Number of moles = 0.05 × 10⁻²°³ mol

Number of molecules:

One mole = 6.022 × 10²³ molecules

0.05 × 10⁻²°³ mol  ×  6.022 × 10²³ molecules / 1 mol

0.30 × 10²⁰°⁷ molecules

3.0 × 10¹⁹°⁷ molecules which is almost equal to 3.0 × 10²⁰ molecules.