Gas Laws
Gas Laws
The fundamental laws of gases or volumetric laws are the following: gas laws chemistry
- Avogadro’s Law: gas laws chemistry
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- Avogadro discovers in 1811 that at constant pressure and temperature, the same amount of gas has the same volume regardless of the chemical element that forms it.
- The volume ( V ) is directly proportional to the amount of gas particles ( n ) independent of the chemical element that forms the gas
- Therefore: V 1 / n 1 = V 2 / n 2
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- Which has the consequence that:
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- If you increase the amount of gas, you increase the volume
- If the amount of gas decreases, the volume decreases
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- Boyle’s Law:
- Boyle discovered in 1662 l to pressure exerted by a gas is inversely proportional to its volume at constant temperature and gas amount: P = k / V → P · V = k (k is a constant). gas laws chemistry
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- Therefore: P 1 · V 1 = P 2 · V 2
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- Which has the consequence that: gas laws chemistry
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- If the pressure increases the volume decreases
- If the pressure decreases the volume increases
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- Note : It is also called the Boyle-Mariotte Law as he discovered it independently in 1676 .
- Charles Law: gas laws chemistry
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- Charles discovered in 1787 and l volume of gas is directly proportional to the temperature at constant pressure: V = k · T (k is a constant).
- Therefore: V 1 / T 1 = V 2 / T 2
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- Which has the consequence that:
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- If the temperature increases the volume increases
- If the temperature decreases the volume decreases
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- Note : Also called Charles and Gay-Lussac’s Law.
- Gay Law – Lussac:
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- Gay-Lussac discovers in 1802 that the pressure of the gas is directly proportional to its temperature at constant volume: P = k · T (k is a constant).
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- Therefore: P 1 / T 1 = P 2 / T 2
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- Which has the consequence that: gas laws chemistry
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- If the temperature increases the pressure increases
- If the temperature decreases the pressure decreases
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- Ideal Gas Law: gas laws chemistry
- Ideal gases have the following properties:
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- Gas molecules move at high speeds in a linear but disorderly manner
- The speed of the gas molecules is proportional to their absolute temperature
- The gas molecules exert sustained pressure on the walls of the container that contains it.
- The collisions between the gas molecules are elastic so they do not lose kinetic energy
- The attraction / repulsion between gas molecules is negligible gas laws chemistry
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- For these ideal gases the following law is fulfilled:
P · V = n · R · T
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- Where n are the moles of the gas and R the universal constant of the ideal gases. gas laws chemistry
- General Gas Law: gas laws chemistry
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- The General Gas Law consists of the union of the following laws:
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- Boyle ‘s law: P 1 · V 1 = P 2 · V 2
- Gay-Lussac’s Law: P 1 / T 1 = P 2 / T 2
- Charles Law: V 1 / T 1 = V 2 / T 2
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- All of them are condensed into the following formula:
P 1 · V 1 / T 1 = P 2 · V 2 / T 2
- Graham’s Law:
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- Formulated by Graham discovered in 1829:
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- The rates of effusion (exit through pores) and diffusion (expansion until occupying the volume of the container) of gases are inversely proportional to the square root of their molar masses: gas laws chemistry
v 1 / v 2 = ( M 2 / M 1 ) -1/2
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- where: v 1 , v 2 are the diffusion / effusion masses of the gas and M 2, M 1 are the molar masses
- Dalton’s Law:
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- Formulated by Dalton in 1801.
- The total pressure of a gas mixture is equal to the sum of the pressures exerted by each of the gases that compose it.
- The pressure exerted by each gas in the mixture is called Partial Pressure. Therefore this law can be expressed as:
P Total = p 1 + p 2 + … + p n
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- Where p 1 , p 2 , …, p n are the partial pressures of each of the gases in the mixture. gas laws chemistry
- Henry’s Law:
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- Made by Henry in 1803.
- The amount of gas dissolved in a liquid at constant temperature is proportional to the partial pressure of the gas above the liquid.
- This law is summarized in the following equation:
p = k H · c
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- Where: p : partial pressure of the gas, c : concentration of the gas and k H : Henry’s constant. gas laws chemistry