Chapter Two-Chemical Quantities Flashcards
Fill in the blank. One atom of _________________ is assigned a mass of 12u. The masses for all other atoms are defined by their relationship to _________________.
Carbon-12
True or False. The mass of an atom is expressed in atomic mass units (amu or u), which is a relative measurement defined by the mass of carbon-11.
False. The mass of an atom is expressed in atomic mass unites (amu or u), which is a relative measurement defined by the mass of carbon-12.
Fill in the blank. One must consider _________________________, which is the relative amount in which each isotope is present in an element. It can be expressed as a percent or a decimal.
ISOTOPIC ABUNDANCE
Define average atomic mass.
averages of the masses of all the element’s isotopes (takes into account the abundance of each isotope within the element; it is the ,ass given on the PT). All isotopes plus the abundance of each isotope.
Fill in the blank. The mole is the ______________________.
Chemist’s Dozen; a word given to an amount in chemistry
True or False. One mole of a substance contains 6.02x10^23 particles (Avogadro’s constant).
True.
Are the words, particles and molecules interchangeable in a mole question?
You betcha!
Define molar mass.
the mass of one mole of a substance
Fill in the blanks. You can use your understanding of the relationship between ______________ and number of particles to see how chemical equations communicate information about how many moles of _________________ and reactants are involved in a ______________.
A) Moles
B) Products
C) Reaction
To do so, one must look at ratios (the coefficients for balanced chemical equations)
True or False. Coefficients in a chemical equation represent the number of particles as well as the moles.
True.
Fill in the blank. The relationship between moles in a balanced chemical equation is called ___________________.
MOLE RATIOS
Define limiting reagent.
the reactant that is completely consumed in the reaction.
Define excess reagent.
the reactant that is not consumed in the reaction.
True or False. The excess reactant determines how much product is produced.
False. The limited reactant determines how much product is produced.
Fill in the blanks. Chemists use __________________ to predict the amount of product that can be expected from a chemical rxn. The amount of product that is predicted by stoichiometry is called the ___________________________.
A) Stoichiometry
B) Theoretical yield
Fill in the blanks. Theoretical yield, however is not always the same as the amount of ________________ that is actually obtained from a _______________________________. The amount of _________________ that is obtained in an experiment is called the _____________________.
A) Product
B) Chemical Reaction
C) Product
D) Actual Yield
Define percentage yield.
the actual yield of a reaction , expressed as a percent of the theoretical yield.
Define theoretical yield.
the amount of product that is produced by a chemical reaction as predicted by the stoichiometry of the chemical equation.
State the law of definite proportions.
The elements in a chemical compound are always present in the same proportions by mass.
True or False. The law of proportions does imply that the elements in a chemical compound are always present in the same proportions by mass.
False. The law of proportions does not imply that the elements in a chemical compound are always present in the same proportions by mass.
Define percent composition.
the relative mass of each element in a compound.
Give an example of compounds that have the same elements but are composed differently.
Water and hydrogen peroxide have the same elements but re composed differently. One way to describe these compounds is by percent composition.
What does ‘empirical’mean?
Empirical means found by experimentation
True or False. Empirical formula is defined as the simplest formula of a compound. It demonstrates smallest whole numbers ratio of atoms in the compound.
Ex. C1H1=(CH)x=(CH)n
True.
Define molecular formula.
it is the actual formula of a compound. It demonstrated the actual number of atoms in a compound.
What is the relation between molecular and empirical formula?
The MF is a multiple of EF
What is the empirical formula used for?
It is used to determine the Molecular (actual) Formula of the compound.
True or False. Chemists use Percentage Composition or Mass Data in their analyses with the ultimate goal to determine an actual formula for an unknown compound.
True.
