How many moles of water are in 1.23 times 10^18 water molecules

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

We have the final answer as

Hope this helps you

 The number  of liter   of  hydrogen gas  that are formed   at STP is  

15.344 L

 calculation

2 Na   +2 H₂O →  2NaOH  +H₂

 calculate  the  moles of   Na

moles  =mass/molar mass

from periodic table the molar mass of Na =  23 g/mol

moles = 31.5 g /23 g /mol  = 1.37  moles

From  equation above the   mole   ratio  of  Na: H2   is  2:1  

therefore the  moles of H2  =1.37 x1/2 =0.685  moles

At  STP  1  moles  of a gas  = 22.4 L

              0.685   moles  =  ?  L

by cross multiplication

=[ (0.685  moles  x 22.4 L) /  1  mole  =15.344 L

The  percent   yield       = 84.77%

calculation

4 Na + O₂   →   2 Na₂O

%yield  =actual yield / theoretical  yield  x 100

Actual  yield=  61.8 g

 The theoretical  yield  is calculated as  below

Step  1:  find the  moles  of Na

     moles =  mass /molar mass

 from periodic table the  molar mass  of Na = 23 g/mol

moles = 54.1 g /23 g/mol =2.352  moles

Step 2: use the  mole ratio to determine  the  moles  of Na₂O

 Na:Na₂O  is  4: 2  therefore the moles of Na₂O = 2.352  x 2/4 =1.176 moles

Step 3:   find  the theoretical mass  of Na₂O

mass =  moles  x  molar  mass

The molar mass  of Na₂O =  [(23 x 2 ) + 16]  =62 g/mol

mass  = 1.176 moles   x 62 g/mol = 72.9  g

%   yield   is therefore  = 61.8 g /72.9 x 100  = 84.77%