Summary Pearson Edexcel A Level Chemistry (Year 1 and Year 2) - Unit 5 - Formulae, Equations and Amounts of Substance (9CH0)

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)
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○​ “Under the same conditions of temperature and pressure, equal volumes of
different gases contain an equal number of molecules (& vice versa)”


Gas laws
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●​ Boyle’s law: 𝑝1𝑉1 = 𝑝2𝑉2 (𝑝 [𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒] ∝ 𝑉 [𝑣𝑜𝑙𝑢𝑚𝑒]
)
𝑝1 𝑝2
●​ Charles’ law: 𝑇1
= 𝑇2
(𝑝 [𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒] ∝ 𝑇 [𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒])



Ideal gas law
●​ ***
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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:


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