The mole
| English | Chinese | Pinyin |
|---|---|---|
| molecule | 分子 | fèn zǐ |
| mole | 摩尔 | mó ěr |
| amount of substance | 物质的量 | wù zhì dì liàng |
| Avogadro number | 阿伏伽德罗数 | ā fú gā dé luó shù |
| molar mass | 摩尔质量 | mó ěr zhì liàng |
Counting the uncountable
- A single spoonful of water holds more molecules 分子 than there are stars in the universe.
- We can't count them one by one — so we count them in moles 摩尔.
- One mole is just a fixed, huge number of particles.
Mole particle count lab
particles = n x Avogadro constant
Change amount of substance and see particle number scale directly.
The mole
- Amount of substance 物质的量 is an SI base quantity; its unit is the mole (mol).
- One mole contains the Avogadro number 阿伏伽德罗数 of particles: $N_{\text{A}} = 6.02 \times 10^{23}$ per mole.
One mole of water: about 18 mL in the lab, but $6.02 \times 10^{23}$ molecules at the atomic scale.
One mole of a substance contains:
A mole always contains the Avogadro number, $N_{\text{A}} = 6.02 \times 10^{23}$, of particles.
The mole is one of the SI base units.
Yes — amount of substance (mole) is a base quantity, alongside the kilogram, metre, second, ampere and kelvin.
Counting particles
- For $n$ moles, the number of particles is $N = n N_{\text{A}}$.
- Always say what you count — atoms for helium, molecules for $\text{O}_2$.
The pressure derivation considers one molecule's velocity component c_x normal to a face of a cube of gas
A sample contains $3.01 \times 10^{23}$ molecules. How many moles is this?
$n = \dfrac{N}{N_{\text{A}}} = \dfrac{3.01 \times 10^{23}}{6.02 \times 10^{23}} = 0.50\ \text{mol}$.
Molar mass 摩尔质量
- Molar mass $M_{\text{m}}$ is the mass of one mole (in $\dfrac{\text{kg}}{\text{mol}}$).
- Mass of $n$ moles is $M = n M_{\text{m}}$; the mass of one particle is $\dfrac{M_{\text{m}}}{N_{\text{A}}}$.
One mole contains the Avogadro number of particles
The molar mass is the mass of:
Molar mass is the mass per mole; dividing it by $N_{\text{A}}$ gives the mass of one particle.
The mass of a single particle equals the molar mass divided by the ____ constant.
$m_0 = \dfrac{M_{\text{m}}}{N_{\text{A}}}$ — molar mass shared over the $N_{\text{A}}$ particles in a mole.
You've got it
- the mole is an SI base unit; $1\ \text{mol}$ has $N_{\text{A}} = 6.02 \times 10^{23}$ particles
- number of particles $N = n N_{\text{A}}$
- molar mass = mass of one mole; one particle's mass $= \dfrac{M_{\text{m}}}{N_{\text{A}}}$