Avogadro's number is used to convert between moles and atoms (or molecules).

This immediately eliminates two answer choices, since moles and molecules in a sample are both contained in the constant. Atoms in a sample of diatomic gas is also easily related to Avogadro's number, as each molecule in the sample will contain exactly two atoms. Avogadro's number can be used to determine the number of moles, molecules, or atoms in a sample of diatomic gas.

Converting grams in a sample to moles allows us to use Avogadro's number to further convert to molecules.

Partial pressure of a gas is directly related to mole fraction, but cannot be used to determine the moles of gas unless the total moles in the sample is known. Partial pressure represents a relationship between the sample and its particular environment, whereas constants govern conversion between moles, grams, atoms, and molecules. Since partial pressure is not directly related to these terms by a constant, Avogadro's number cannot be applied to partial pressure to determine any useful data.

To solve, we will need to find the mass of one liter of DEET and use the mass percentage of nitrogen to find the mass of nitrogen represented. Then, the atomic mass of nitrogen can be used to convert this to moles, and Avogadro's number can be used to convert to atoms.

First, find the mass of DEET in a one-liter sample:

Find the mass of nitrogen in 998 grams of DEET by finding the percentage of nitrogen by mass:

Use this mass percentage and atomic mass to find the moles of nitrogen in the one-liter sample.

Use Avogadro's number to find the number of atoms in this sample.

An alternative method would be to convert the grams of DEET to moles, and then from moles to molecules. There is one nitrogen atom per molecule of DEET, so this would method also get you the same answer.

The number of atoms in a sample is dependent on the molar quantity, NOT the mass of the sample. Avogadro's number shows that there are  atoms in a mole of any element. Knowing this, we can find out how many moles of the element are represented by the given amount of atoms.

By dividing the mass of the samples by the molar mass of each respective element, we can find which sample has this molar quantity.

Sodium:

Lithium:

Potassium:

As a result, a five-gram sample of sodium has .

A full liter of a one molar solution of sodium hydroxide would contain one mole of sodium ions, or  ions. Here, you have only one tenth the volume, so multiply the number in one mole by one tenth.

Now that we have reduced the volume, we need to account for the concentration.

When finding the empirical formula for a compound, it helps to imagine a 100g sample of the molecule. This way, the percentages of the atoms can be converted to amounts in grams. At this point, dividing each amount by the atom's molar mass results in the values that will be compared to one another in order to find the ratio of atoms in the molecule.

 (carbon)

 (hydrogen)

 (oxygen)

 (nitrogen)

From these calculations, we can set up a ratio.

3.45C : 6.9H : 1.72O : 1.72N

If we divide this ratio by the smallest value (1.72), we can see that it can be reduced.

2C : 4H : 1O : 1N

As a result, the empirical formula for the compound is C₂H₄ON.

4-octene looks like this:

To get an empirical formula, we find the ratio of each element within the compound and make it as low as possible. We have eight carbons and sixteen hydrogens. The ratio of carbons to hydrogens is 8-to-16, which reduces to 1-to-2. The full formula for 4-octene is , and the empirical formula is .

An empirical formula must be written as the most simplified ratio of the elements that the compound contains. For example,  is empirical because it cannot be simplified any further; the ratio of its atoms is 1:1:4.

The formula for glucose, , can be simplified by a factor of six. The empirical formula for glucose would be .

The first step in solving this question is to convert the mass of each element to moles. This can be done by dividing the given mass of each element by the molecular weight of each element.

After finding the moles of each element, you have to find the smallest whole number ratio of each element. The smallest whole number ratio can be found by dividing moles of each element by the lowest mole quantity (in this case,  of oxygen). You are left with  carbons,  hydrogens, and  oxygen. The empirical formula for this compound is .

To find the molecular formula of the compound you need to divide the molecular weight of the actual compound by the molecular weight of the empirical formula. The molecular weight of the empirical formula is:

Dividing the molecular weight of the actual compound () by the molecular weight of empirical formula gives:

This means that the empirical formula must be multiplied by three to get the molecular formula; therefore, the molecular formula is . Compared to the empirical formula, the molecular formula contains more carbon atoms and more oxygen atoms.

The first step in solving this question is to convert the mass of each element to moles. This can be done by dividing the given mass of each element by the molecular weight of each element.

The molecular weight of carbon is , hydrogen is , and oxygen is .

The first step in solving this question is to convert the mass of each element to moles. This can be done by dividing the given mass of each element by the molecular weight of each element.

After finding the moles of each element, you have to find the smallest whole number ratio of each element. The smallest whole number ratio can be found by dividing moles of each element by the lowest mole quantity (in this case,  of oxygen).

You are left with  carbons,  hydrogens, and  oxygen. The empirical formula for this compound is .

An empirical formula is the simplest form of a molecular formula that still retains the ratio of the elements. If a formula can be divided by a whole number, it is a molecular formula and not an empirical formula. A molecular formula is the exact identity of a compound, showing the total number of atoms used to create the compound.

The only given answer that is not divisible by a whole number is , making it an empirical formula. It is also the molecular formula for both acetaldehyde and ethanol, depending on molecular geometry and orientation.