1a Mole Concept Flashcards
What is a proton number?
The proton number of an element is the number of protons in the nucleus of an atom of that element.
What is a nucleon number?
The nucleon number (or mass number) of an element is the total number of protons and neutrons in the nucleus of an atom of the element.
What is a nuclide?
A nuclide is any species of a given mass number and atomic number.
What are isotopes? What does isotopic abundance refer to? How do isotopes differ in chemical and physical properties?
Isotopes are atoms with the same proton number but different nucleon numbers. Isotopic abundance refers to the abundance of each isotope in the mixture in terms of percentages or fractions. Isotopes have the same number of electrons and hence the same chemical properties. However, they have different numbers of neutrons and thus, they have different physical properties.
Define relative atomic mass. Explain why the relative atomic mass of an element may not be close to a whole number.
Relative atomic mass Ar is defined as the average mass of one atom of the element divided by 1/12 the mass of 1 atom of a carbon-12 atom.
The relative atomic mass of an element may not be close to a whole number as the naturally occurring elements often consist of a mixture of isotopes and the relative atomic mass of an element takes into consideration the different isotopes and their relative proportions.
Define the Avogadro constant L. Define a mole.
The Avogadro constant (L mol^-1) is the constant of proportionality between the number of specified entities of a substance (N) and the amount of specified entities of that substance (n mol).
N = L times n
A mole of a substance is the amount of substance that contains 6.02*10^23 elementary entities of that substance. (Note: The elementary entities must be specified and may be atoms, molecules, ions, electrons or other particles or formula units)
Define molar mass and state its units.
The molar mass of a substance is the mass of one mole of the substance and has units g mol^-1.
State whether Ar, Mr and Molar mass has units.
Only the molar mass has units.
Define empirical formula.
The empirical formula of a compound is the formula that shows the simplest whole-number ratio of the atoms of different elements present in one molecule or formula unit of the compound.
Define molecular formula.
The molecular formula of a compound is the formula that shows the actual number of atoms of each element present in one molecule of the compound.
Recall how to determine the empirical formula of a compound using combustion data and percentage composition by mass.
Pg 8 and 9 of notes.
Define stoichiometry. Define stoichiometric amounts.
Stoichiometry is the relationship between the amounts of reactants and products in a chemical reaction. It has to do with how much one substance will react with another.
Stoichiometric amounts are the amounts of substances undergoing reaction as given by a balanced chemical equation.
Define the law of conservation of matter.
The law of conservation of matter states that mass is conserved in all chemical reactions and every atom of every element must be accounted for since they are not destroyed nor created, but rearranged.
Define a limiting reagent.
A limiting reagent is a deficient reactant that is consumed completely in a reaction. (The maximum theoretical yield of a product is determined based on the limiting reactant.)
Define theoretical yield, actual yield and percentage yield.
The theoretical yield of a product refers to the mass of a product calculated from the chemical reaction based on the amount of limiting reagent used.
The actual yield refers to the mass of product that is actually obtained in the reaction during an experiment.
The percentage yield relates the actual yield to the theoretical yield and is expressed as Percentage yield = actual yield/theoretical yield *100%
