Average Atomic Mass and Isotopes

Flashcards created to review concepts related to average atomic mass, isotopes, and solutions as discussed in the lecture.

What is the difference between mass and mass number in chemistry?

Mass is the measure of how heavy an object is, while mass number is the total number of protons and neutrons in an atom.

What is meant by weighted average in the context of average atomic mass?

Weighted average accounts for the different proportions of each isotope in a sample, rather than treating them equally.

What is the mass defect?

The mass defect is the difference between the expected mass of a nucleus (sum of the masses of protons and neutrons) and the actual mass of the nucleus.

How is average atomic mass determined on the periodic table?

Average atomic mass is calculated as the weighted average of the masses of all stable isotopes of an element based on their natural abundance.

What is an AMU?

An AMU, or atomic mass unit, is a unit of mass used to express atomic and molecular weights, defined as one twelfth of the mass of a carbon-12 atom.

How do you calculate the average atomic mass of an element with two isotopes?

Average atomic mass = (fractional abundance of isotope 1 × mass of isotope 1) + (fractional abundance of isotope 2 × mass of isotope 2).

What information does the natural abundance of isotopes provide?

Natural abundance indicates the relative percentages or fractions of each isotope of an element in a typical sample.

How do you convert a percentage to a fractional amount?

To convert a percentage to a fractional amount, move the decimal point two places to the left.

What role does Avogadro's number play in atomic mass calculations?

Avogadro's number (6.022 x 10^23) relates the mass of an atom in grams to the number of atoms in a mole.

What is the difference between a solution's solute and solvent?

The solute is the substance being dissolved, while the solvent is the substance doing the dissolving.

What is molarity?

Molarity is a concentration unit defined as moles of solute per liter of solution.

What is the formula for calculating percent concentration of a solution?

Percent concentration = (mass of solute / mass of solution) × 100.

How do you calculate the amount of solute from a known solution concentration and volume?

Amount of solute = Concentration × Volume of solution.

What is the significance of atomic mass being expressed in both AMU and grams?

Atomic mass in AMU relates to individual atoms, while in grams, it relates to moles of atoms in a sample.

Explain why you cannot simply add the mass numbers of protons and neutrons to find the mass of an atom in practice.

When protons and neutrons come together in a nucleus, some mass is converted to energy, resulting in a lower actual mass than the sum of individual nucleons.