Modern States Unit 2 Flashcards
What is a crucial topic in chemistry that deals with the amounts of substances?
Stoichiometry
What are important concepts that help determine stoichiometric amounts
Molar and formula masses
Coefficients in chemical reactions do not indicate ratios of reactants and products in terms of what?
masses
What is calculated by multiplying the molar mass of the substance by the number of moles?
the mass of a substance produced
What is the unit of measurement for amount of substance, a quantity proportional to the number of elementary entities of a substance?
The mole
What type of reagent is the reactant that is present in the smallest amount?
Limiting Reagent
What type of reagent is whatever is remaining after the reaction?
Excess reagent
What type of reagent is the one with leftover moles after the reaction?
Excess reagent
Balancing chemical reactions involves ensuring that the numbers of each type are what?
are the same on both sides of the reaction
What type of reagent gets completely used up in the reaction?
Limiting Reagent
What type of reagent determines the outcome of the reaction?
Limiting Reagent
Coefficients in chemical reactions indicate ratios in terms of what?
molecules or moles
Coefficients in chemical reactions do not indicate what in terms of molecules or moles, not masses?
ratios of reactants and products
Aqueous solutions involve dissolving substances in what?
water
What occurs when ionic substances dissolve in water, producing more ions that conduct electricity?
Dissociation
What type of electrolytes dissociate completely?
Strong
What type of electrolytes only conduct electricity to a limited extent
weak
Understanding the formula and dissociation of substances can help calculate the what of ions in a solution
concentration
For what type of substances, the formula represents the numbers and types of atoms composing a single molecule of
the substance?
covalent
What type of compounds are composed of discrete cations and anions combined in ratios to yield electrically neutral bulk matter?
Ionic compounds
what traits are the identity of a substance is defined by?
- types of atoms or ions it contains
- the quantity of each type of atom or ion
How formula mass for an ionic compound is calculated in the same way as the formula mass for covalent compounds
by summing the average atomic masses of all the atoms in the compound’s formula
formula for ionic compound doesn’t represent composition of a discrete molecule, so it may
not correctly be referred to as the molecular mass
True or false
Formula mass for an ionic compound is not calculated in the same way as the formula mass for covalent.
False
The amount of product that may be produced by a reaction under specified conditions is called what?
as calculated per the
stoichiometry of an appropriate balanced chemical equation
theoretical yield
What is defined as the amount of substance containing
the same number of discrete entities as the number of atoms in a sample of pure
12C weighing exactly 12 g?
(such as atoms, molecules, and ions)
A mole
The number of entities composing a mole is a constant is properly reported with an explicit unit of “per mole,” a conveniently rounded version being What?
6.022 × 1023/mol
fundamental constant named Avogadro’s number (NA) or the Avogadro constant in honor of Italian scientist Amedeo Avogadro.
True or False
1 mole of any element contains the same number of atoms as 1 mole of any other element.
True
The masses of 1 mole of different elements, however, are different, since the masses of the
individual atoms are drastically different.
What is defined as the percentage by
mass of each element in the compound
percent composition
empirical formulas are derived from experimentally measured element masses by what three steps?
- Deriving the number of moles of each element from its mass
- Dividing each element’s molar amount by the smallest molar amount to yield subscripts for a tentative
empirical formula - Multiplying all coefficients by an integer, if necessary, to ensure that the smallest whole-number ratio of subscripts is obtained
Molecular formulas are derived how?
by comparing the compound’s molecular or molar mass to its empirical formula
mass
What is empirical formula mass ?
the sum of the average atomic masses of all the atoms represented in an empirical formula
If we know the molecular (or molar) mass of the substance, we can divide this by the empirical formula mass units per molecule
empirical formula
molecular or molar mass (amu or g per mol)
/
empirical formula mass (amu or g per mol)
= n formula units or molecule
The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as
what?
stoichiometric amounts
The amount of product obtained is called the what?
actual yield
forlmula of percent yield
percent yield = actual yield/
theoretical yield × 100%
What is quantitative analysis?
the determination of the amount
or concentration of a substance in a sample
he described approach to measuring vinegar strength was an early version of the analytical technique known as
what?
titration analysis
A typical titration analysis involves the use of what?
a buret
special dyes called what are added to the sample solutions to impart a change
in color at or very near the equivalence point of the titration
indicators
the volume of titrant actually measured is called the what?
end point
Name reasons why the reaction’s actual yield is smaller than the theoretical yield.
- no reaction actually ever goes 100% to completion
- there is experimental error in recovering all of the product.
- the chemical reaction is not 100% efficient
What is a way were a sample is subjected to some treatment that causes a change in the physical
state of the analyte that permits its separation from the other components of the sample?
gravimetric analysis
The elemental composition of hydrocarbons and related compounds may be determined via a gravimetric method known as what?
combustion analysis
In a what, a weighed sample of the compound is heated to a high temperature under a stream of oxygen gas, resulting in its complete combustion to yield gaseous products of known
identities.
combustion analysis
The substances undergoing reaction are called what and their formulas are placed on which side of the
equation.
reactants
the left
The substances generated by the reaction are called what, and their formulas are placed on which sight
of the equation
products
the right
The relative numbers of reactant and product species are represented by what?
(numbers placed immediately to the left of each formula)
A coefficient of 1 is typically omitted.
coefficients
True or false
Substances with relatively large solubilities are said to be soluble in water
True
balanced meaning that equal numbers of atoms for each element
involved in the reaction are represented on the reactant and product sides
meaning that equal numbers of atoms for each element
involved in the reaction are represented on the reactant and product sides
What are ions whose presence is required to maintain charge neutrality
spectator ions
Define solubility
The extent to which a substance may be dissolved is quantitatively expressed
What reaction is one in which dissolved substances react to form one (or more) solid products.
precipitation
Many reactions of this type involve the exchange of ions between ionic compounds in aqueous solution and are sometimes referred to as double displacement, double replacement, or metathesis reactions.
A substance will precipitate when solution conditions are what?
conditions are
such that its concentration exceeds its solubility
Substances with relatively low solubilities are said to be what and these are the substances that readily precipitate from solution?
insoluble
What is a substance that will dissolve in water to yield hydronium ions
acid
Acids that completely dissolve in water to yield hydronium ions are called what?
strong acid
What only partially react with water, leaving a large
majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions
weak acids
hydroxides that completely dissociate in
water, are considered what?
strong bases
What is a specific type of acid-base reaction in which the reactants are an acid and a base, the
products are often a salt and water, and neither reactant is the water itself
A neutralization reaction
These equations show that Na atoms lose electrons while Cl atoms (in the Cl2 molecule) gain electrons, the “s”
subscripts for the resulting ions signifying they are present in the form of a solid ionic compound.
half-reaction
species that is oxidized
reducing agent
species that is reduced
oxidizing agent
1.loss of electrons
2.gain of electrons
oxidation
reduction
What is an element in
a compound is the charge its atoms would possess if the compound was ionic
oxidation number (or oxidation state)
What are those in which one or more elements involved undergo a change in oxidation
number
Oxidation-reduction (redox) reactions
What reactions are redox reactions in which an ion in solution is displaced (or
replaced) via the oxidation of a metallic element?
Single-displacement (replacement)
Define:
spontaneous process
a process that occurs under specified conditions without the requirement of energy from some external source
The formation of a solution is an example of a spontaneous
What is the thing that is produced when the strengths of the intermolecular forces of attraction between solute and solvent species in a solution are no
different than those present in the separated components, the solution is formed with no accompanying energy change?
an ideal solution
What is a stepwise process
in which energy is consumed to overcome solute-solute and solvent-solvent attractions (endothermic processes) and released when solute-solvent attractions are established?
the formation of a solution
When some substances are dissolved in water, they undergo either a physical or a chemical change that yields ions
in solution. These substances constitute an important class of compounds called what?
electrolytes
Substances that do not
yield ions when dissolved are called what?
nonelectrolytes
If the physical or chemical process that generates the ions is essentially 100% efficient (all of the dissolved compound yields ions), then the substance is known as a what?
strong electrolyte
If only a relatively small fraction of the dissolved substance undergoes the ion-producing process, it is
called a what?
weak electrolyte
The electrostatic attraction between
an ion and a molecule with a dipole is called what?
an ion-dipole attraction
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution
because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This
process represents a physical change known as what?
dissociation
The solubility of a solute in a particular solvent is the maximum concentration that may be achieved under given
conditions when the what happens?
dissolution process is at equilibrium
When a solute’s concentration is equal to its solubility, the solution is said to be what?
saturated
If the solute’s concentration is less than its solubility, the solution is said to be what?
unsaturated
