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.
In the closed system, the mass of substances before and after chemical reaction is constant. It can call Lavoisier’s Law (Mass Conservation Law)
Problem 1a. 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.
SolutionBecause 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 :
7.62/2.54 gram x 1.54 gram = 4.62 gram
gram
Problem 2
b. Four grams of copper reacts exactly with 2 grams of sulfur to form copper sulfide. What is grams of copper sulfide can be formed if 10 grams of copper and 10 grams of sulfur reacted?
Solution
