5 - Formulae, equations and amounts of substance
● ***Mole: unit for amount of a substance
● ***Empirical formula: simplest whole-number ratio of atoms of each element in
compound
● ***Molecular (real) formula: gives total number of atoms of each element in each
molecule/formula unit of a substance
●
Avogadro’s law
● Avogadro constant (L): 6.02 x 1023/mol
𝑉 (1𝑠𝑡 𝑔𝑎𝑠 𝑣𝑜𝑙𝑢𝑚𝑒) 𝑉2 (2𝑛𝑑 𝑔𝑎𝑠 𝑣𝑜𝑙𝑢𝑚𝑒) 3
● *** 𝑛1 (1𝑠𝑡 𝑔𝑎𝑠 𝑛𝑜. 𝑚𝑜𝑙) = 𝑛2 (2𝑛𝑑 𝑔𝑎𝑠 𝑛𝑜. 𝑚𝑜𝑙)
(= 24 𝑑𝑚 ) (molar volume in RTP)
1
○ “Under the same conditions of temperature and pressure, equal volumes of
different gases contain an equal number of molecules (& vice versa)”
Gas laws
1
● Boyle’s law: 𝑝1𝑉1 = 𝑝2𝑉2 (𝑝 [𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒] ∝ 𝑉 [𝑣𝑜𝑙𝑢𝑚𝑒]
)
𝑝1 𝑝2
● Charles’ law: 𝑇1
= 𝑇2
(𝑝 [𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒] ∝ 𝑇 [𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒])
Ideal gas law
● ***
3
𝑝 (𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 [𝑃𝑎]) × 𝑉 (𝑣𝑜𝑙𝑢𝑚𝑒 [𝑚 ]) = 𝑛 (𝑛𝑜. 𝑚𝑜𝑙) × 𝑅 (𝑔𝑎𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡) × 𝑇 (𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 [𝐾])
𝑤ℎ𝑒𝑟𝑒 𝑅 = 8. 31 (𝐽/𝐾 𝑚𝑜𝑙)
● An ideal gas is one in which:
1
● ***Mole: unit for amount of a substance
● ***Empirical formula: simplest whole-number ratio of atoms of each element in
compound
● ***Molecular (real) formula: gives total number of atoms of each element in each
molecule/formula unit of a substance
●
Avogadro’s law
● Avogadro constant (L): 6.02 x 1023/mol
𝑉 (1𝑠𝑡 𝑔𝑎𝑠 𝑣𝑜𝑙𝑢𝑚𝑒) 𝑉2 (2𝑛𝑑 𝑔𝑎𝑠 𝑣𝑜𝑙𝑢𝑚𝑒) 3
● *** 𝑛1 (1𝑠𝑡 𝑔𝑎𝑠 𝑛𝑜. 𝑚𝑜𝑙) = 𝑛2 (2𝑛𝑑 𝑔𝑎𝑠 𝑛𝑜. 𝑚𝑜𝑙)
(= 24 𝑑𝑚 ) (molar volume in RTP)
1
○ “Under the same conditions of temperature and pressure, equal volumes of
different gases contain an equal number of molecules (& vice versa)”
Gas laws
1
● Boyle’s law: 𝑝1𝑉1 = 𝑝2𝑉2 (𝑝 [𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒] ∝ 𝑉 [𝑣𝑜𝑙𝑢𝑚𝑒]
)
𝑝1 𝑝2
● Charles’ law: 𝑇1
= 𝑇2
(𝑝 [𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒] ∝ 𝑇 [𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒])
Ideal gas law
● ***
3
𝑝 (𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 [𝑃𝑎]) × 𝑉 (𝑣𝑜𝑙𝑢𝑚𝑒 [𝑚 ]) = 𝑛 (𝑛𝑜. 𝑚𝑜𝑙) × 𝑅 (𝑔𝑎𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡) × 𝑇 (𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 [𝐾])
𝑤ℎ𝑒𝑟𝑒 𝑅 = 8. 31 (𝐽/𝐾 𝑚𝑜𝑙)
● An ideal gas is one in which:
1
