why sum of molefractions is always one??please explain
Answers
In chemistry, the mole fraction or molar fraction (xi) is defined as the amount of a constituent (expressed in moles), ni, divided by the total amount of all constituents in a mixture (also expressed in moles), ntot:[1]
{\displaystyle x_{i}={\frac {n_{i}}{n_{\mathrm {tot} }}}} {\displaystyle x_{i}={\frac {n_{i}}{n_{\mathrm {tot} }}}}
The sum of all the mole fractions is equal to 1:
{\displaystyle \sum _{i=1}^{N}n_{i}=n_{\mathrm {tot} };\;\sum _{i=1}^{N}x_{i}=1} {\displaystyle \sum _{i=1}^{N}n_{i}=n_{\mathrm {tot} };\;\sum _{i=1}^{N}x_{i}=1}
The same concept expressed with a denominator of 100 is the mole percent or molar percentage or molar proportion (mol%).
The mole fraction is also called the amount fraction.[1] It is identical to the number fraction, which is defined as the number of molecules of a constituent Ni divided by the total number of all molecules Ntot. The mole fraction is sometimes denoted by the lowercase Greek letter χ (chi) instead of a Roman x.[2][3] For mixtures of gases, IUPAC recommends the letter y.[1]
The National Institute of Standards and Technology of the United States prefers the term amount-of-substance fraction over mole fraction because it does not contain the name of the unit mole.[4]
Whereas mole fraction is a ratio of moles to moles, molar concentration is a quotient of moles to volume.
The mole fraction is one way of expressing the composition of a mixture with a dimensionless quantity; mass fraction (percentage by weight, wt%) and volume fraction (percentage by volume, vol%) are others.