cises
Answer the following questions.
A. State and explain Avogadro's law.
Answers
Explanation:
Avogadro’s law is named after the Italian scientist Amedeo Carlo Avogadro, who suggested that two dissimilar ideal gases occupying the same volume at a given (constant) temperature and pressure must contain an equal number of molecules.
Formula and Graphical Representation
At constant pressure and temperature, Avogadro’s law can be expressed via the following formula:
V ∝ n
V/n = k
Where V is the volume of the gas, n denotes the amount of gaseous substance (often expressed in moles), and k is a constant. When the amount of gaseous substance is increased, the corresponding increase in the volume occupied by the gas can be calculated with the help of the following formula:
V1/n1 = V2/n2 ( = k, as per Avogadro’s law).
The graphical representation of Avogadro’s law (with the amount of substance on the X-axis and volume on the Y-axis) is illustrated below.
Avogadro's Law Graph
Here, the straight line (which indicates that the two quantities are directly proportional) passes through the origin, implying that zero moles of gas will occupy zero volume.
Derivation
Avogadro’s law can be derived from the ideal gas equation, which can be expressed as follows:
PV = nRT
Where,
‘P’ is the pressure exerted by the gas on the walls of its container
‘V’ is the volume occupied by the gas
‘n’ is the amount of gaseous substance (number of moles of gas)
‘R’ is the universal gas constant
‘T’ is the absolute temperature of the gas
Rearranging the ideal gas equation, the following equation can be obtained.
V/n = (RT)/P
Here, the value of (RT)/P is a constant (since the temperature and pressure kept constant and the product/quotient of two or more constants is always a constant). Therefore:
V/n = k
Thus, the proportionality between the volume occupied by a gas and the number of gaseous molecules is verified.
Molar Volume of a Gas
As per Avogadro’s law, the ratio of volume and amount of gaseous substance is a constant (at constant pressure and temperature). The value of this constant (k) can be determined with the help of the following equation:
k = (RT)/P
Under standard conditions for temperature and pressure, the value of T corresponds to 273.15 Kelvin and the value of P corresponds to 101.325 kilo Pascals. Therefore, the volume occupied by one mole of a gas at STP is:
Volume occupied by 1 mole of gas = (8.314 J.mol-1.K-1)*(273.15 K)/(101.325 kPa) = 22.4 litres
Therefore, one mole of any gaseous substance occupies 22.4 litres of volume at STP.
Examples of Avogadros Law
The process of respiration is a great example of Avogadro’s law. When humans inhale, the increase in the molar quantity of air in the lungs is accompanied by an increase in the volume of the lungs (expansion of the lungs). An image detailing the change in volume brought on by an increase in the number of gaseous molecules is provided below.
Example of Avogadro's Law
Another common example of Avogadro’s law is the deflation of automobile tyres. When the air trapped inside the tyre escapes, the number of moles of air present in the tyre decreases. This results in a decrease in the volume occupied by the gas, causing the tyre to lose its shape and deflate.
Answer:
Avagadros law states that equal volumes of all gases at the same temperature and pressure have the same number of molecules.for a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.
Explanation:
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