Chapter 3

Question 1

What is stoichiometry?

Answer 1

an area of study that examines the quantities of substances consumed and produced in chemical reactions

Question 2

What represents heat in a chemical equation?

Answer 2

delta

Question 3

What are three types of reactions?

Answer 3

combination - 2 reactants form 1 product, based on what we know

decomposition - substance breaks down into two or more substances (opposite of combination) A -> B+C

combustion - burning! C -> CO2, H -> H2O; rapid reactions that produce a flame; most often involve oxygen in the air as a reactant

Question 4

What do metal carbonates give off (decompose) when heated?

Answer 4

CO2 and a metal oxide

Question 5

What is molecular weight (MW)?

Answer 5

the sum of the atomic weights for the atoms in a chemical formula
-for an element (like sodium, Na) the formula weight is the atomic weight (22.99 g/mol)
-for an ionic compound, use the empirical formula
-if the substance is a molecule, the molecular weight is also called its formula weight (FW) or molar mass (mass of 1 mol of a substance)

Question 6

How do you find the percentage of the mass of a compound that comes from each of the elements in the compound (percent composition)?

Answer 6

this equation:
%element = (# of atoms)(atomic weight)/(molar mass of the compound) x 100%

Question 7

What is Avogadro’s number?

Answer 7

1 mole = 6.022x10^23 things
Avogadro’s number is the number of atoms, ions, or molecules in one mole of these particles
#atoms of an element in a mole = the subscript in a formula (#atoms of that element in the formula) times Avogadro’s number

Question 8

How do you use the empirical formula?

Answer 8

1. assume 100. grams of your chemical
2. % mass becomes mass, convert to moles
3. divide by smallest number of moles
4. if a # is not a whole #, multiply by 2 or 3 or 4 so all #s are whole (do for all #s)
5. put your whole numbers with your elements

Question 9

How do you determine something’s molecular formula?

Answer 9

of atoms in a molecular formula is a multiple of the number of atoms in an empirical formula
if we find the empirical formula and know a molar mass (molecular weight) for the compound, we can find the molecular formula
(molar mass given/molar mass of empirical formula)
multiply each subscript by this number

Question 10

How and when do you use the binary naming system?

Answer 10

(can only have 2 elements)
use if the 1st element is a nonmetal or metalloid, there are no charges in the binary system
1. the name of the element farther to the left in the periodic table (closest to the metals) is usually written first
2. if both elements are in the same group, the one closer to the bottom of the table is named first
3. the name of the second element is given an -ide ending
4. Greek prefixes indicate the # of atoms of each element (not used with the 1st element)

Question 11

What are the Greek prefixes for the binary system?

Answer 11

mono- 1
di- 2
tri- 3
tetra- 4
penta- 5
hexa- 6
hepta- 7
octa- 8
nona- 9
deca- 10

Question 12

How and when do you use the ionic naming system?

Answer 12

names of ionic compounds consist of the cation name followed by the anion name
1. cations
a. cations formed from metal atoms have the same name as the metal
b.if a metal can form cations with different charges, the positive charge is indicated by a roman numeral in parentheses following the name of the metal
c. cations composed of nonmetal atoms have names that end in -ium
2. anions
a. the names of monatomic anions are formed by replacing the ending of the name of the element with -ide
b. polyatomic anions containing oxygen have names ending in either -ate or -ite and are called oxyanions
c. anions derived by adding H+ to an oxyanion are named by adding as a prefix the word hydrogen or dihydrogen, as appropriate

Question 13

How do you name inorganic acids?

Answer 13

1. acids containing anions whose names end in -ide are named by changing the -ide ending to -ic, adding the prefix hydro- to this anion name, and then following with the word acid
2. acids containing anions whose names end in -ate or -ite are named by changing -ate to -ic and -ite to -ous, then adding the word acid

Question 14

What do coefficients in balanced equations show?

Answer 14

-relative number of molecules of reactants and products
-relative nnumber of moles of reactants and products, which can be converted to mass

Question 15

How do you compare two different materials from a chemical equation?

Answer 15

use the mole ratio from the balanced chemical equation
1. convert grams known to moles
2. mole ratio - use coefficients from the balanced equation
3. convert moles unknown to grams unknown

Question 16

What is a limiting reactant?

Answer 16

the reactant present in the smallest stoichiometric amount; the other is the excess reagent (used to determine amounts of products that are produced and amounts of any other reactant(s) that are used in a reaction)

Question 17

What is the theoretical yield?

Answer 17

the maximum amount of product that can be made (amt of product possible as calculated through the stoichiometry problem)

Question 18

What is the actual yield?

Answer 18

the amount of product that one actually produces and measures (as opposed to theoretical yield)

Question 19

What is percent yield (what is the formula)?

Answer 19

%yield = actual yield/theoretical yield x 100%

Question 20

know acid nomenclature