Question

A scientist has 207.45g of H2O in a beaker. How many water molecules are in the beaker?

Answer 1

Answer:

6.94 x 10²⁴molecules

Explanation:

Given parameters:

Mass of water  = 207.45g

Unknown:

Number of molecules  = ?

Solution:

To solve this problem, we must understand:

      1 mole of a substance  contains 6.02 x 10²³ molecules

Now, first find the number of moles of water;

 Number of moles  = $\frac{mass}{molar mass}$  

 Molar mass of water  = 2(1) + 16  = 18g/mol

  Number of moles  = $\frac{207.45}{18}$   = 11.53moles

So;

          1 mole of a substance  contains 6.02 x 10²³ molecules

       11.53moles of carbon dioxide will contain 11.53 x  6.02 x 10²³

                                                                 = 6.94 x 10²⁴molecules