Q072 - Physics For Engineers And Scientists - Solutions ON7AMI Amateur Radio, Meteology and Astronomy website. JO10UX # 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.

In :
# 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


 سُوۡرَةُ حٰمٓ السجدة / فُصّلَت ثُمَّ اسْتَوَىٰ إِلَى السَّمَاءِ وَهِيَ دُخَانٌ فَقَالَ لَهَا وَلِلْأَرْضِ ائْتِيَا طَوْعًا أَوْ كَرْهًا قَالَتَا أَتَيْنَا طَائِعِينَ ﴿١١ فَقَضَاهُنَّ سَبْعَ سَمَاوَاتٍ فِي يَوْمَيْنِ وَأَوْحَىٰ فِي كُلِّ سَمَاءٍ أَمْرَهَا ۚ وَزَيَّنَّا السَّمَاءَ الدُّنْيَا بِمَصَابِيحَ وَحِفْظًا ۚ ذَٰلِكَ تَقْدِيرُ الْعَزِيزِ الْعَلِيمِ ﴿١٢ Surah Fussilat: Thereafter turned He to the heaven and it was as smoke, and said Unto it and Unto the earth: come ye twain, willingly or loth. They said: we come willingly. (11) Then He decreed them as seven heavens in two days, and revealed Unto each heaven the command thereof; and We bedecked the nether heaven with lamps and placed therein a guard. That is the ordinance of the Mighty, the Knower. (12) De hemelen en aarde (waren) een samenhangende massa. Wij hebben ze toen van elkaar gescheiden… Wij hebben de hemel tot een beschermend dak gemaakt … en de dag en de nacht, de zon en de maan geschapen. (Koran 41 11:12) Copyright (c) 2000-2020 - Jean Paul Mertens - ON7AMI - formal ON1AMI - Grote Steenweg 86 - 9840 Zevergem - Belgium - Europe