Someone who is good in chemistry please help.

2.0×10⁻⁶ mol

Prefix = (2)  

exponent = (-6)

Explanation:

Given data:

Number of molecules of water = 1.23×10¹⁸ molecules

Number of moles of water = ?

Solution:

Avogadro number:

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.

1 mole = 6.022 × 10²³ molecules of water

1.23×10¹⁸ molecules × 1 mol / 6.022 × 10²³ molecules

0.20×10⁻⁵ mol

2.0×10⁻⁶ mol

Prefix = (2)  

exponent = (-6)