摩尔分数和质量分数之间的差异

Key Difference – Mole Fraction vs Mass Fraction

摩尔分数和质量分数用于表达化合物中不同组分之间的比率。The key difference between mole fraction and mass fraction is that mole fraction deals with themolesof different components of a compound whereas mass fraction deals with themassesof different components in a compound. Mole fraction can be converted into the mass fraction of the same compound and vice versa.

内容

1.Overview and Key Difference
2.What is Mole Fraction
3.什么是质量分数
4.Similarities Between Mole Fraction and Mass Fraction
5.Side by Side Comparison – Mole Fraction vs Mass Fraction in Tabular Form
6.概括

What is Mole Fraction?

摩尔分数是由痣数量表达的混合物中的组件量之间的比率。它是组成部分的摩尔与混合物中所有成分的摩尔之和之间的比率。它可以如下。

Mole fraction = moles of a constituent/sum of moles of all constituents (mass of the mixture)

或

X_i= n_i/ n_全部的

The mole fractions of all components equals 1 since the mole fraction is a ratio. The mole fraction can be used to express the mole percentage by multiplying the mole fraction from 100. The mole fraction can also be called the amount fraction because moles give the amount of a constituent. Mole fraction is unit-less since it is a ratio between moles (units cancel out).

Calculation of Mole Fraction

Let us consider a sample problem to understand what mole fraction is.

Question:

当将0.1 mol NaCl溶解在100克纯水中时，找到NaCl的摩尔分数。

Answer:

Number of moles of water = 100 g / 18 gmol^-1

= 5.56 mol

Sum of moles of all constituents = 0.1 (NaCl) + 5.56 (H₂O)

= 5.66 mol

南汽的摩尔分数l = 0.1 mol/ 5.66 mol

= 0.018

质量分数是多少?

质量分数是组成部分的质量与混合物的总质量之间的比率。Since it is a ratio between masses, the mass fraction is unit-less (units cancel out). It can be given as an equation (given below).

Mass fraction = mass of a constituent/sum of masses of all constituents (mass of the mixture)

或

W_i= m_i/ m_全部的

由于质量分数为比率，因此所有组件的质量分数等于1。单个组件的质量分数总是低于1。质量分数也可以作为质量百分比。在这里，质量分数乘以100。在元素分析计算中，质量分数是指化学元件与化合物的质量之间的比率。质量分数与温度无关，因为当温度改变时质量不会改变。

Calculation involving Mass Fraction

Question:

Find the mass of sucrose in a solution of sucrose (500 g) in which water is having mass fraction of 0.65.

Answer:

Total mass of the mixture = 500 g

Mass fraction of water = 0.65

Then the mass fraction of sucrose = 1-0.65 = 0.35

The mass of sucrose = 0.35 x 500g

= 175克

What are the Similarities Between Mole Fraction and Mass Fraction?

• Both terms express ratios.
• 摩尔分数和质量分数都是无单位术语。
• Both gives values that are either equal or less than 1.
• Both are independent of temperature changes.

What is the Difference Between Mole Fraction and Mass Fraction?

Mole Fraction vs Mass Fraction
Mole fraction is the ratio between the moles of a constituent and the sum of moles of all constituents in a mixture.	质量分数是组成部分的质量与混合物的总质量之间的比率。
Components
使用成分的摩尔计算摩尔分数。	Mass fraction is calculated using masses of constituents.

概括– Mole Fraction vs Mass Fraction

Mole fraction and mass fraction are used to express the relative fractions of different constituents in a mixture. Both are unit-less terms since the ratios have the same unit, and thus the units cancel out. The key difference between mole fraction and mass fraction is that mole fraction deals with the moles of different components of a compound whereas mass fraction deals with the masses of different components in a compound.

Reference:

1. “Mole Fraction.” Wikipedia, Wikimedia Foundation, 12 Mar. 2018,Available here.
2. “Mole Fraction”, Chemsteam,Available here.
3.“质量分数（化学）。”Wikipedia，Wikimedia基金会，2018年3月3日，Available here.

Image Courtesy:

1. “Salt mole fraction” By Jzana – Own work(CC BY-SA 3.0)viaCommons Wikimedia