Stoichiometry and the Mole

This set of flashcards covers key vocabulary and concepts related to stoichiometry, significant figures, isotopes, and the mole.

Significant Figures

Digits in a number that contribute to its precision, showing the accuracy of a measurement.

Exact Numbers

Numbers obtained through counting that have an infinite number of significant figures.

Approximate Numbers

Numbers obtained through measurement that have a limited precision.

Captive Zeros

Zeros between non-zero digits that are always considered significant.

Leading Zeros

Zeros that precede all non-zero digits, which are never significant.

Trailing Zeros

Zeros at the end of a number; they are significant only if the number has a decimal point.

Addition & Subtraction Rule for Sig Figs

The result should have the same number of decimal places as the measurement with the least decimal places.

Multiplication & Division Rule for Sig Figs

The result should have the same number of significant figures as the measurement with the least significant figures.

Scientific Notation

A way of expressing numbers as a number between 1 and 10 multiplied by a power of 10.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Atomic Mass Unit (u)

A unit of mass used to express atomic and molecular weights, defined as one twelfth of the mass of carbon-12.

Isotopic Abundance

The relative amount of each isotope of an element found in nature.

Average Atomic Mass

The weighted average of the atomic masses of an element's isotopes, reflecting their relative abundances.

Molar Mass

The mass of one mole of a substance, expressed in grams per mole (g/mol).

Avogadro's Number

The number of representative particles in one mole, approximately equal to $6.022 imes 10^{23}$.

Molar Volume

The volume occupied by one mole of an ideal gas at STP, which is $22.4 ext{ L}$.

Unit Analysis (Factor Analysis)

A method used to convert between units using conversion factors.

Quantitative Measurements

Measurements that represent a definite amount and are usually expressed in numbers with units.

Qualitative Measurements

Measurements that describe the quality of something and are often expressed in words.

Accuracy

How close a measurement is to the true value.

Precision

How reproducible a measurement is; the consistency of repeated measurements.