Question 72 - Review - Chapter 1

Problem:

Given is 1 liter of water.

Question:

a) How many molecules are there in the water?
b) How many hydrogen atoms?
c) How many oxygen atoms?

Solution:

The formula of water is $ H_{2} O $

So per molecule of water we have two hydrogen atoms and one oxygen atom.

# Berekeningen
import scipy.constants as physics
from mendeleev import O, H

N_A = physics.value('Avogadro constant')

print(f'The atomic weight of {O.name} is {O.atomic_weight}.')
print(f'The atomic weight of {H.name} is {H.atomic_weight}.')
H2O_ag = O.atomic_weight + 2*H.atomic_weight
print(f'The molecular weight of water is therefore {O.atomic_weight} + 2 * {H.atomic_weight} = {H2O_ag}')

aantal_molecules = N_A * 1000 / H2O_ag
print(f'The number of molecules in 1 kg of water (= 1Liter) is Avogadro / Molecular weight (in g) times 1000 (in kg)')
print('')
print(f'\ta): {N_A} * 1000 / {H2O_ag}) = {aantal_molecules:5.3g} ')
print('')
print(f'\tb): There are {aantal_molecules:5.3g} oxigen atoms')
print('')
print(f'\tc): There are twice as much {(aantal_molecules):5.3g} * 2 = {(aantal_molecules *2):5.3g} hydrogen atoms')

The atomic weight of Oxygen is 15.999.
The atomic weight of Hydrogen is 1.008.
The molecular weight of water is therefore 15.999 + 2 * 1.008 = 18.015
The number of molecules in 1 kg of water (= 1Liter) is Avogadro / Molecular weight (in g) times 1000 (in kg)

	a): 6.022140857e+23 * 1000 / 18.015) = 3.34e+25 

	b): There are 3.34e+25 oxigen atoms

	c): There are twice as much 3.34e+25 * 2 = 6.69e+25 hydrogen atoms