Final answer:
The total mass of the mixture should be the sum of the individual masses of the substances combined, according to the Law of Conservation of Mass. It should be 24.2 g for a mixture of 12.8 g and 11.4 g substances. The result should also consider the accuracy of the measurement represented by significant figures.
Step-by-step explanation:
When mixing substances, the total mass of the mixture should be the sum of the individual masses of the substances, according to the Law of Conservation of Mass. Therefore, if you have 12.8 g of one substance and 11.4 g of another, the total mass of the combination should be 12.8 g + 11.4 g = 24.2 g. If the measured mass of the mixture does not reflect this sum, it suggests an issue with either the measurement process or the actual mixing process. However, it's also important to consider significant figures in the reported measurement. The mass measurement should be rounded to the least number of decimal places of the combined substances.
The Law of Definite Proportions states that a chemical compound always contains exactly the same proportion of elements by mass. When compounds react, they do so in a mass ratio that is a simple whole number, as exemplified by the reaction of 1 gram of A with 8 grams of B producing 9 grams of C. This reflects both the Law of Definite Proportions and the Law of Conservation of Mass.