SCH3U Test #3 (Ch. 5, 6, 7) Flashcards
Define anhydrous
A term used to describe a compound that does not have any water molecules bonded to it; applies to compounds that can be hydrated.
What is a carbon-hydrogen combustion analyzer?
It is a device that uses the combustion enabling properties of oxygen gas to determin the composition of compounds containing hydrogen, carbon and another element like oxygen.
Define empirical formula
Shows the lowest whole number ratio of atoms of each element in a compound.
What is a hydrate?
This is a compound that has a specific number of water molecules bonded to each formula unit.
What does the Law of Definite Proportions state?
It states that the elements in a chemical compound are always present in the same proportions by mass.
Define mass percent
The mass of a solute divided by the mass of the solution, expressed as a percent.
What is a molecular formula?
A formula that shows the actual number of atoms of each element in a molecule or formula unit.
Define percentage composition
The relative mass of each element in a compound.
Define Average atomic mass
The average of the masses of all the isotopes of an element; given in atomic mass units (u)
Define Isotopic abundance
The relative amount of an isotope of an element; expressed as a percent or a decimal fraction.
Define mole
The SI base unit for amount of substance; contains the same number of atoms, molecules, or formula units as exactly 12 g of carbon-12.
Define weighted average
An average that takes into account the abundance or importance of each value.
Define Avogadro constant
The experimentally-determined number of particles in 1 mol of a substance; the currently accepted value is 6.022 141 99x10^23
Define mass spectrometer
An instrument that uses magnetic fields to separate the isotopes of an element and measure the mass and abundance of each isotope.
Define molar mass
The mass of 1 mol of a substance, numerically equal to the element’s average atomic mass; expressed in g/mol.
Actual yield
The measured quantity of product obtained in a chemical reaction.
excess reactant
The reactant that remains after a reaction is over.
mole ratios
Ratios that compare the number of moles of different substances in a balanced chemical equation.
percentage yield
The actual yield of a reaction, expressed as a percent of the theoretical yield.
coefficient
In a balanced chemical equation, a positive number that is placed in front of a formula to show how many units of the substance are involved.
competing reactant
A reaction that occurs at the same time as a principal reaction and consumes the reactants and/or the products of the principal reaction
limiting reactant
The reactant that is completely consumed during a chemical reaction, limiting the amount of product produced.
percentage purity
The percent of a sample that is composed of a specific compound or element.
stoichiometric amounts
The exact molar amounts of a reactant or a product, as predicted by a balanced chemical equation.
stoichiometry
The study ofthe mass-mole-number relationships in chemical reactions and formulas.
theoretical yield
The amount of product that is produced by a chemical reaction as predicted by the stoichiometry of the chemical equation.
