Unit 1: Topic 1 - Moles & Molar Mass

Question 1

In a lab setting, which property is measured to avoid counting individual particles?

Answer 1

We find the masses of substances because it would be impossible to count each particle. To determine the number of particles in a substance, we must perform calculations involving molar mass and Avogadro’s number.

Question 2

What is a mole?

Answer 2

The mole is a scientific unit used to measure a large number of particles, such as atoms or molecules within a substance.

Question 3

What is Avogadro’s number, and what does it represent?

Answer 3

Avogadro’s number, or 6.022E23, represents the number of particles in one mole of a substance. Regardless of the mass of each particle in a substance, which varies based on composition, one mole of that substance contains 6.022E23 particles.

For instance, one mole of hydrogen contains 6.022E23 atoms, and one mole of water contains 6.022E23 molecules.

Question 4

What is atomic mass unit?

Answer 4

The atomic mass of an element is expressed in atomic mass units (amu). Both the mass of a proton and that of a neutron are about 1 amu, whereas the mass of an electron is negligible and thus is counted as 0 amu. As a result, the atomic mass of an element is roughly equal to the sum of the number of protons and the number of neutrons in an atom of that element.

Question 5

What is molar mass, and how do we find it?

Answer 5

The molar mass is the mass in grams of one mole of a substance. The units are grams per mole, and you can find the molar mass of each element on the periodic table under each symbol.

To find the molar mass of a compound, multiply the molar mass of each element within the compound by the number of atoms of that element, then add all of the resulting values up. The relationship between the number of moles and the mass can be represented by n = m/M, where n = number of moles, m = mass, and M = molar mass.”