Chapter Two-Chemical Quantities

Question 0

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 _________________.

Answer 0

Carbon-12

Question 1

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.

Answer 1

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.

Question 2

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.

Answer 2

ISOTOPIC ABUNDANCE

Question 3

Define average atomic mass.

Answer 3

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.

Question 4

Fill in the blank. The mole is the ______________________.

Answer 4

Chemist’s Dozen; a word given to an amount in chemistry

Question 5

True or False. One mole of a substance contains 6.02x10^23 particles (Avogadro’s constant).

Answer 5

True.

Question 6

Are the words, particles and molecules interchangeable in a mole question?

Answer 6

You betcha!

Question 7

Define molar mass.

Answer 7

the mass of one mole of a substance

Question 8

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 ______________.

Answer 8

A) Moles
B) Products
C) Reaction
To do so, one must look at ratios (the coefficients for balanced chemical equations)

Question 9

True or False. Coefficients in a chemical equation represent the number of particles as well as the moles.

Answer 9

True.

Question 10

Fill in the blank. The relationship between moles in a balanced chemical equation is called ___________________.

Answer 10

MOLE RATIOS

Question 11

Define limiting reagent.

Answer 11

the reactant that is completely consumed in the reaction.

Question 12

Define excess reagent.

Answer 12

the reactant that is not consumed in the reaction.

Question 13

True or False. The excess reactant determines how much product is produced.

Answer 13

False. The limited reactant determines how much product is produced.

Question 14

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 ___________________________.

Answer 14

A) Stoichiometry

B) Theoretical yield

Question 15

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 _____________________.

Answer 15

A) Product
B) Chemical Reaction
C) Product
D) Actual Yield

Question 16

Define percentage yield.

Answer 16

the actual yield of a reaction , expressed as a percent of the theoretical yield.

Question 17

Define theoretical yield.

Answer 17

the amount of product that is produced by a chemical reaction as predicted by the stoichiometry of the chemical equation.

Question 18

State the law of definite proportions.

Answer 18

The elements in a chemical compound are always present in the same proportions by mass.

Question 19

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.

Answer 19

False. The law of proportions does not imply that the elements in a chemical compound are always present in the same proportions by mass.

Question 20

Define percent composition.

Answer 20

the relative mass of each element in a compound.

Question 21

Give an example of compounds that have the same elements but are composed differently.

Answer 21

Water and hydrogen peroxide have the same elements but re composed differently. One way to describe these compounds is by percent composition.

Question 22

What does ‘empirical’mean?

Answer 22

Empirical means found by experimentation

Question 23

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

Answer 23

True.

Question 24

Define molecular formula.

Answer 24

it is the actual formula of a compound. It demonstrated the actual number of atoms in a compound.

Question 25

What is the relation between molecular and empirical formula?

Answer 25

The MF is a multiple of EF

Question 26

What is the empirical formula used for?

Answer 26

It is used to determine the Molecular (actual) Formula of the compound.

Question 27

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.

Answer 27

True.