Chemistry
State the 'law of conservation of mass'. State the main points of Landolt's experiment for experimental evidence of the law. State the limitations of the law.
Matter
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Answer
Law of conservation of mass
Law of conservation of mass states that whenever a chemical change takes place, the total mass of the reacting substances is exactly equal to the total mass of the products, [provided masses are measured under similar conditions].
Main points of Landolt's experiment
- In an 'H' shaped tube as shown in the figure, Landolt introduced a solution of sodium chloride [NaCl] and silver nitrate [AgNO3] in the limbs of the tube and sealed it and weighed it.
- The solutions were mixed by shaking to obtain a white precipitate of silver chloride.
- The tube was again weighed after the experiment.
Result : Weight of H tube + reactants = Weight of H tube + products.
Hence, total mass of reactants = total mass of products
Limitations of the law
- Chemical energy stored up in the reactants is released in the form of heat and light.
- Hence, mass is converted to energy and thus mass and energy are to be considered together.
- Hence, a very slight error in the experiment was observed.
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