Pure Substances and Empirical Formulas

Flashcards based on the lecture notes covering pure substances, empirical formulas, and laboratory practices.

What is the Law of Definite Composition?

A given compound always contains the same, fixed ratio of elements.

What is the mole ratio used for in pure substances?

It is used to calculate how many of each element is present in a sample.

How many H atoms are in one molecule of H2O?

2 H atoms.

How many O atoms are in one molecule of H2O?

1 O atom.

What does the empirical formula represent?

The simplest whole-number ratio of elements in a compound.

In the empirical formula calculation, what is the first step using percent composition?

Convert the percentages to grams, assuming 100 grams of the compound.

What is the percent composition of a hydrate of Na2CO3 if it weighs 4.31 g before heating and 3.22 g after?

You would need to calculate based on the mass loss during heating.

What is the importance of knowing the empirical formula?

It allows scientists to understand the simplest relationship of atoms in a compound.

What sample mass of iron was used to determine its empirical formula after rusting?

0.691 g.

What final mass of the compound was found after the rusting of iron?

1.000 grams.