Chemistry: Representative Particles and Moles

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Questions and Answers

What is a representative particle?

The smallest unit into which a substance can be broken down without a change in composition, usually atoms, molecules, formula units or ions.

What is the representative particle for an element?

Atom

What is the representative particle for diatomic molecules and molecular compounds?

Molecule

What is the representative particle for ionic compounds?

Formula Unit Signup and view all the answers

A mole is a ______.

count Signup and view all the answers

What is Avogadro's number?

6.02 x 10²³ Signup and view all the answers

What does molar mass refer to?

The mass of a mole of any substance. Signup and view all the answers

In order to calculate molar mass, what must you do?

Find the number of grams of each element and then add them together. Signup and view all the answers

When the problem is already in moles, you can convert it straight to ______ without the use of Avogadro's number.

grams Signup and view all the answers

When going from a representative particle to grams, you must first find _.

molar mass Signup and view all the answers

The volume of a gas is usually measured at _ and .

standard temperature and pressure Signup and view all the answers

What is the standard temperature?

0°C Signup and view all the answers

What is the standard pressure?

1 atmosphere (atm) Signup and view all the answers

At STP, 1 mol of any gas occupies a volume of _______ L.

22.4 Signup and view all the answers

What is the molar volume of a gas?

22.4 L Signup and view all the answers

The density of a gas is usually measured in the units ______.

g/L Signup and view all the answers

The density of a gas at STP is used to calculate the _ _ of that gas.

molar mass Signup and view all the answers

What is an empirical formula?

Gives the lowest whole number ratio of elements in a compound. Signup and view all the answers

What is a molecular formula?

Either the same as the empirical formula or some whole number multiple of it. Signup and view all the answers

What is percent composition?

Percent by mass of each element in a compound. Signup and view all the answers

Study Notes

Representative Particles

Smallest unit of a substance, which can be atoms, molecules, formula units, or ions.
For an element, the representative particle is an atom, the fundamental unit retaining elemental properties.
Diatomic molecules (e.g., N₂, O₂) and molecular compounds have representative particles known as molecules, composed of neutral atoms acting as a unit.
Ionic compounds' representative particles are formula units, the lowest whole number ratio of ions in the compound.

Moles and Avogadro's Number

A mole is a counting unit used in chemistry to represent a specific quantity of particles.
Avogadro's number, 6.02 x 10²³, is the number of particles in one mole, used for converting between moles and atoms.

Molar Mass

Molar mass is defined as the mass of one mole of any substance.
To calculate molar mass, add the masses of each element in a compound, based on their respective grams.

Molar Conversions

Converting moles to grams does not require Avogadro's number if the problem is already expressed in moles.
To convert from a representative particle to grams, determine the molar mass first.

Gas Properties

At standard temperature and pressure (STP: 0°C and 1 atm), one mole of any gas occupies 22.4 liters.
Molar volume of gas is consistently 22.4 L at STP.

Gas Density

The density of a gas is measured in g/L and is crucial for determining molar mass.

Empirical and Molecular Formulas

Empirical formula represents the lowest whole number ratio of elements in a compound.
A molecular formula may be identical to the empirical formula or a whole number multiple of it.

Percent Composition

Percent composition is the mass percentage of each element in a compound, calculated using the formula: % comp = (grams of element / grams of compound) x 100.

Example Calculations

Example for empirical formula determination shows ratio calculations from mass percentages to obtain the simplest whole number representation.
Determination of molecular formula utilizing mass percentages and empirical formula confirmations, including molar mass comparison.

Formula Units Calculations

Example of the calculation of representative particles from moles, addressing the conversion of moles of a compound to the number of specific ions present.

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Description

Explore the concept of representative particles in chemistry with these flashcards. Learn about the smallest units of substances, including atoms and molecules, that retain their elemental properties. This quiz will enhance your understanding of moles and the structure of matter.