Direction : In the following questions, a statement of assertion (A) ...
Avogadro’s law states that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules. This empirical relation can be derived from the kinetic theory of gases under the assumption of a perfect (ideal) gas. The law is approximately valid for real gases at sufficiently low pressures and high temperatures. At STP, all gas have same volume for 1 mol of gas and that volume is always equal to the 22.4 L.
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Direction : In the following questions, a statement of assertion (A) ...
Assertion: One mole of molecules has mass equal to gram molecular mass and contains Avogadro’s number of molecules or has a volume of 22.4 L at STP if the substance is a gas.
Reason: One mole of an ionic compound has mass equal to gram formula unit mass and contains Avogadro’s number of formula units.
Explanation:
- The assertion states that one mole of molecules has a mass equal to the gram molecular mass. This is true because one mole of any substance contains Avogadro’s number of particles, which is approximately 6.022 x 10^23. The gram molecular mass is the molar mass of the substance expressed in grams. Therefore, one mole of molecules has a mass equal to the gram molecular mass.
- The assertion also states that one mole of molecules contains Avogadro’s number of molecules or has a volume of 22.4 L at STP (standard temperature and pressure) if the substance is a gas. This is also true because at STP, one mole of any ideal gas occupies a volume of 22.4 L. This is known as molar volume.
- The reason states that one mole of an ionic compound has a mass equal to the gram formula unit mass and contains Avogadro’s number of formula units. This is also true because one mole of any ionic compound contains Avogadro’s number of formula units, which is equal to the number of ions present in the compound. The gram formula unit mass is the molar mass of the compound expressed in grams.
- Therefore, both the assertion and the reason are true, but the reason is not the correct explanation of the assertion. The reason provides additional information about the mass and number of formula units in one mole of an ionic compound, but it does not explain why one mole of molecules has a mass equal to the gram molecular mass or why one mole of molecules has a volume of 22.4 L at STP if the substance is a gas.
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