Atoms, Molecules, and Stoichiometry Flashcards

Vocabulary flashcards for key concepts in Atoms, Molecules, and Stoichiometry.

Atoms

Tiny invisible particles of an element that cannot be created or destroyed.

Molecules

A group of atoms held together by covalent bonds.

Relative Atomic Mass (Ar)

An average mass of an atom or an element compared with 1/12 of the mass of atom 12C.

Relative Molecular Mass (Mr)

An average mass of a molecule compared with 1/12 of the mass of atom 12C.

Avogadro's Constant (L)

Defined as the number of carbon atoms in exactly 12 g of carbon-12 which is 6.02 x 10^23.

Mole

Defined as the amount of substance containing Avogadro’s number of particles of that substance.

Empirical Formula

The simplest formula which shows the ratio of the atoms of the different elements in the compound.

Molecular Formula

A formula which shows the actual number of atoms of each element present in one molecule of a compound.

Stoichiometry Reaction

In a balanced chemical equation, the total number of atoms before and after the reaction must be the same. The coefficient in the balanced equation indicates the relative amount (measured in moles) of the reactants and products.

Excess Reagents

Reactants that are not completely reacted at the end of the reaction.

Limiting Reagents

Reactants that are completely reacted at the end of the reaction and determine the yield of the product.

Theoretical Yield

The maximum mass of product that can be obtained.

Actual Yield

Actual mass of product obtained, which may be less due to incomplete reaction or product loss.

Concentration of Solution

The concentration of an aqueous solution expressed as moldm-3 or gdm-3.

Molar Volume

The volume occupied by 1 mol of substance at STP or RTP.

RTP

Room Temperature and Pressure defined by the IUPAC as an absolute pressure of 101.3kPa and a temperature of 298K (25°C)

STP

Standard Temperature and Pressure defined by the IUPAC is an absolute pressure of 101.3kPa and a temperature of 273K (0°C)

Oxidation

The loss of electrons

Reduction

The gain of electrons

Oxidising Agent

The reactant that causes oxidation and is itself reduced in the process.

Reducing Agent

The reactant that causes reduction and is itself oxidised in the process.

Disproportionation

Both oxidation and reduction of the same element occurs; element is simultaneously oxidised and reduced.

Real Gas Deviation

Plots of pV against p show a deviation from ideal behavior because there are strong forces of attraction between the molecules like hydrogen bonding and van der waals.

Partial Pressure

The pressure due to any individual component in a gas mixture; ptot = px + py+ pz … where px , py and pz represent the partial pressures.