Compounds and Stoichiometry (4)

Question 1

Empirical formula

Answer 1

the smallest whole-number ratio of the elements in a compound.

(Empirical formula for benzene is CH, molecular is C6H6, ionic compounds will only have empirical formula).

Question 2

Molecular formula

Answer 2

Either the same as or a multiple of the empirical formula; it gives the exact number of atoms of each element in a compound.

Question 3

Percent composition

Answer 3

To calculate, determine the mass of the individual element and divide by the molar mass of the compound.

% composition = mass of element in formula / molar mass x 100

Question 4

Combination rxn

Answer 4

occurs when two or more reactants combine to form one product.
2H2 + O2 –> 2H2O

Question 5

Decomposition rxn

Answer 5

occurs when one reactant is chemically broken down into two or more products.
2HgO –> 2Hg + O2

Question 6

Combustion rxn

Answer 6

occurs when a fuel and an oxidant ( typically oxygen) react, forming the products water and carbon dioxide.

CH4 + 2O2 –> CO2 + 2H2O

Question 7

Single - Displacement Rxn

Answer 7

occurs when an atom or ion in a compound is replaced by an atom or ion of another element.

Cu + AgNO3 –> Ag + CuNO3

Question 8

Double - Displacement Rxn

Answer 8

elements from two different compounds swap places with each other to form two new compounds.

CaCl2 + 2AgNO3 –> Ca(NO3)2 + 2AgCl

Question 9

Neutralization rxn

Answer 9

acid reacts with base to produce salt and water

HCl + NaOH –> NaCl + H2O

Question 10

Percent Yield

Answer 10

Actual / Theoritical x 100

Question 11

Electrocytes

Answer 11

Ionic compounds make good electrolytes b/c they dissolve most readily. Nonpolar covalent compounds are the weakest b/c they do not form current-carrying ions.

HCl
MgBr2

Question 12

-ous and -ic endings

Answer 12

• ous endings can also be used to indicate lesser charge
• ic endings indicate greater charge

(Fe2+ Ferrous)
(Fe3+ Ferric)

Question 13

-ide

Answer 13

Monotomic anions ends with -ide

F- flouride
(O2- Oxide)

Question 14

-ite and -ate endings

Answer 14

-ite the one with less oxygen
-ate the one with more oxygen
(NO2- = nitrite , SO3 2- = sulfite )
(NO3- = nitrate , SO4 2- = sulfate)

Question 15

-Hypo and - per endings

Answer 15

ClO- = hypochlorite
ClO2- = chlorite
ClO3- = chlorate
ClO4- = perchlorate

Question 16

Gram equivalent weight (GEW)

Answer 16

Molar mass / n

n = quantitiy of interest (equivalent) (electron or H+ or OH-)

Question 17

Equivalents

Answer 17

Mass of compound (g) / Gram equivalent weight (g) (GEW)

Question 18

Normality (N)

Answer 18

the measure of concentration given in the units equivalents/liter

Molarity (mol/L) = Normality (equiv/L) / n

Question 19

1 mol of any ideal gas at STP

Answer 19

22.4L

Question 20

Limiting reagent

Answer 20

the reactant that will be consumed first in a chemical reaction.

All limiting reagent problems must be done in units of moles.

It is the rate at which the reactant is consumed, combined with absolute mole quantities determines which reactant is the limiting reactant.

Question 21

Excess reagent

Answer 21

other reactant presents.