Answer:
A. The law of definite proportions states that all pure samples of a particular chemical compound contain the same elements combines in the same proportion by mass.
B. The law of conservation of mass states that during ordinary chemical reactions, matter can neither be created or destroyed.
Note: The full question is as follows;
A researcher placed 25.0 g of silver chloride, AgCl, in sunlight and allowed the substance to decompose completely to form silver, Ag, with the release of chlorine gas, Cl2. The gas was collected in a container during the decomposition. The researcher determined that the mass of the silver formed was 18.8 g, and the mass of the chlorine gas formed was 6.2 g. The equation for the reaction is:
2AgCl ----> 2Ag + Cl2
a. State the law of definite proportions. Then use the researcher's data to confirm the law of definite proportions. Show your calculations.
b. State the law of conservation of matter. Then use the researcher's data to confirm the conservation of matter. Show your calculations.
Explanation:
A. Mass of silver obtained from AgCl = 18.8g.
Percentage mass of silver in the chloride = (18.8/25.0) * 100 = 75.2 %
Mass of chlorine obtained from AgCl = 6.2
Percentage mass of chlorine = (6.2/25) * 100 = 24.8 %
In one mole of AgCl with a molar mass of 143.3 g/mol; mass of silver = 107.8, mass of Cl = 35.5
Percentage mass of Ag = (107.8/143.3) * 100 = 75.2%
Percentage mass of Cl = (35.5/143.3) * 100 = 24.8%
Since the percentages by mass of Ag and AgCl obtained from the sample is the same to that obtained from a mole of AgCl, the law of definite proportions which states that all pure samples of a particular chemical compound contain the same elements combined in the same proportion by mass is verified.
B. Mass of reactant; AgCl sample = 25.0
Mass of products; At = 18.8 g; Cl = 6.2 g
Sum of products masses = 18.8 + 6.2 = 25.0 g
Therefore mass of reactant = mass of products.
This is in accordance with the law of conservation of mass which states that during ordinary chemical reactions, matter is neither created nor destroyed.
