Mass and Proportion Laws: Conservation of Mass, Definite Proportions, and Multiple Proportions

Flashcards covering conservation of mass, the law of definite proportions, and the law of multiple proportions with examples.

What does the law of conservation of mass state?

The total mass of the system does not change in a chemical reaction.

What does the law of definite proportions state?

A given chemical compound always contains the same proportion of elements by mass.

In the first water sample (3.06 g H, 27.35 g water), what is the percentage of hydrogen by mass?

11.2%.

According to the law of definite proportions, what should be true about the hydrogen percentage in any water sample?

It remains the same (11.2%).

What does the law of multiple proportions state?

If two elements form a series of compounds, the ratio of the masses of the second element that combines with a constant mass of the first element can be reduced to small whole numbers.

In the iron–sulfur example, with 1 g of iron, the sulfur masses are 1.148 g (FeS2) and 0.574 g (FeS). What is the sulfur mass ratio?

2:1.

What does keeping the first element's mass constant mean in the law of multiple proportions?

We compare compounds formed with the same fixed mass of the first element (e.g., 1 g of iron).

Does the law of multiple proportions specify the exact formulas of compounds?

No; it only requires that the ratio of the second element's mass to the fixed first element mass be a simple whole-number ratio.

What does RXN stand for in the notes?

Reaction.