Doubts regarding Mole concept and Avogadros number [closed]








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So I am really confused about simple topics like mole and Avogadro
Here is my oversimplified view


So mass of 1 atom of elements in grams was not in whole numbers and it was difficult using em for calculations for ex (avg) atomic mass of carbon is 2.6566962 × 10^-23 g g, weight of hydrogen atom is 1.6735575 × 10^-24 g, mass of carbon is 1.9944235 × 10^-23 g. (these were measured using mass spectrometer


So one way was to use a different unit instead of gram. Elements could be measured relative to each other. So mass of one atom on an element could be assigned 1 and others could have mass relative to that


So scientists decided to assign Carbon which is an element with 6p 6n and 6e a value of 12u
since electron has negligible weight as compared to proton and neutron which are almost equal in weight, it can be said


1u~ mass of 1 proton + 1 neutron = mass of 2 neutron or proton
Note:i know that mass of an element cannot be said as sum of mass of its subatomic particles because when subatomic particles come together to form the element some mass is released in form of energy but we will ignore that for simplicity


1 amu = 1.66054e-24 g


q)i have a question y is carbon used to define amu then why not say that 1 amu is equal to 1/16 the mass of oxygen or 1/20 the mass of neon, is it because carbon is found quite commonly


q)is the current value of amu the most ideal, would it be better if the value of amu was instead double of what it is? Basically what would be the problem if any if hydrogen was given the value 2u and others were relative to it.


**Now coming to Avogadro's number/constant/mole**


So like there's dozen which is defined as group of 12, usually used to measure fruits/bananas
why 12? because Twelve is convenient because it has the most divisors of any number under its double, a property only true of 1, 2, 6, 12, 60, 360, and 2520.


So Scientists needed a term to describe a group of atoms/molecules/subatomic particles
since it almost impossible to measure mass of 1 atom of different elements u could instead measure a large constant number of atoms of elements
This was called mole now u had to decide the value of mole it couldnt be 10 100 or 100000 as they were too small


So they decided that the number of atoms of carbon(it goes without saying 12C) in 12g of Carbon will be used as a standard and they named the number obtained Avogadro's Number


So in simpler terms mole is


Lets says u have 1 oxygen atom (which has 8 electrons 8 protons and 8 neutrons) mass of 16u = 16 \* 1.66054e-24 g. If u take 6.022 \* 1023 of sch oxygen atoms then then the mass will be equal to 16g


how does this makes sense/ what is the the correct explanation


what is the need of mole if the ratio of masses of atoms of two elements remains same irrespective of the number of atoms


what does gas laws have to do with avogadros constant


what is the difference between avogadros number and constant and why doesnt one of em have a unit per mole


Some of the questions might be dumb but i will be really grateful if someone could help me out




I will try to answer to your first question, related to the choice of a reference atom.


The choice of the reference atom for measuring atomic masses has been a long and tedious discussion that had lasted during the whole $20$th century. There has been plenty of congresses devoted to this choice. In the beginning the reference was Hydrogen, which was given the value $1.00000$. After some time, there was doubt about the proportion of $\ce{^2H}$ or deuterium in hydrogen, which was changing from spot to spot on the planet, so that the H atom had not the same mass everywhere.. So after a couple of congresses, the scientists decided to replace hydrogen by $1/16$ of the mass of oxygen as a reference for atomic masses. Later on, there was also difficulty about the proportion of the isotope $\ce{^{18}O}$. So, after many congresses, scientists decided to choose the isotope $\ce{^{12}C}$ so that the unit of atomic mass is $1/12$ times the mass of this $\ce{^{12}C}$ isotope. Why to choose this one (and not another isotope) was a hard discussion, where solving technical difficulties had an important part. I cannot enter this discussion, which would take hours to develop, because there was ass many possibilities as the number of atoms available. So please take it for granted. It is not important to know the series of reasons that had been used to convince the specialists of mass spectrometry about the choice of $\ce{^{12}C}$


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