Question

How many moles of water, H2O, contain 2.0×1022 molecules of water? (See the hints for assistance in interpreting scientific notation.)
Express the quantity in moles to two significant figures.

Answer 1

Moles of H2O = 2 x 10^22
                         ---------------------
                          6.02 x 10^23
 
                      =          0.033 moles.

Answer 2

Answer : The number of moles of water is, $3.3\times 10^{-2}$

Solution : Given,

Number of water molecules = $2.0\times 10^{22}$

As we know that 1 mole of water molecule contains $6.022\times 10^{23}$ number of water molecules.

As, $6.022\times 10^{23}$ number of water molecules present in 1 mole  of water molecule

So, $2.0\times 10^{22}$ number of water molecules present in $\frac{2.0\times 10^{22}}{6.022\times 10^{23}}=3.3\times 10^{-2}$ mole  of water molecule

Therefore, the number of moles of water is, $3.3\times 10^{-2}$