Mass Conservation Law (Lavoisier’s Law)

Look at the burning process of paper !!! Is there decompression of mass in this process??? The most of product in the burning process of paper is gases, so the mass of substances become fewer than before. If the process occur in the closed system, so that the mass of substances before and after chemical reactions is constant.

According to Lavoisier, combustion of substances at an opened place cause the substance absorb or release other substance from and into the air, so that it cause change of the substance mass. But, in the close place there are no other substances absorbed or released during the reaction, so that mass of the object is constant relative.

Law of Conservation of Matter: During an ordinary chemical change, there is no detectable increase or decrease in the quantity of matter.

Problem 1

a. 1 gram of sodium exactly to react with 1.54 grams of chlorine gas produce sodium chloride. Calculate mass of chloride gas required to produce 7.62 grams of sodium chloride.

Solution

Because of sodium exactly to react with chlorine, then,

Sodium chloride produced = sodium mass + chlorine mass

                                               = 1 gram + 1.54 gram

                                               = 2.54 gram

To produce 7.62 grams of sodium chloride is required chlorine as much as :

                      7.62 gram x 1.54 gram = 4.62 gram

                      2.54 gram

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