GENERAL CHEMISTRY EXAM 2 QUESTIONS WITH CORRECT ANSWERS

GENERAL CHEMISTRY EXAM 2
QUESTIONS WITH CORRECT
ANSWERS



How to find the mass of a molecule? - Correct Answers -g molecule --> mol molecule --
> Avogadro's #

Example:

(1 mol CO.01g CO2)
x
(6.022 x 10^23 CO2 molecules / 1 mol CO2)

OR (to organize the equation/steps)

(44.01g CO mol CO2)
x
(1 mol CO.022 x 10^23 CO2 molecules)

Mass Percent Composition
(Mass Percent) - Correct Answers -(Mass of element X in 1 mol of compound /
Mass of 1 mol of the compound) x 100%

Example:

(2 x molar mass Cl / molar mass CCl2F2) x 100%

How to calculate the number of moles of each element that are present in each sample?
- Correct Answers -Example:

0.857g H x (1 mol H / 1.01 g H) = 0.849 mol H

6.86g O x (1 mol O / 16.00g O) = 0.429 mol O

[Divide each # of moles by fewest moles]

0.849 mol H / 0.429 = 1.98 => 2

,0.429 mol O / 0.429 = 1

So, the empirical compound of Hydrogen and Oxygen is H2O

How to calculate Molecular Mass [n]
(After finding Empirical Formula and given Molar Mass in the problem)? - Correct
Answers -Molecular Mass [n] =>

(molar mass / empirical formula molar mass)

Elemental Analysis - Correct Answers -A method of obtaining Empirical Formulas for
unknown compounds (containing C and H) by burning a sample of the compound in
pure oxygen and analyzing the products of the combustion reaction.

What must be in equilibrium in a "balanced" chemical reaction? - Correct Answers -1.)
The number of atoms

2.) The amount of mass

Organic Compounds - Correct Answers -A compound composed of C and H and other
elements: N, O, and S.

Example: Methane (CH4)

Hydrocarbons - Correct Answers -Organic Compounds composed of only C and H.

Alkanes, Alkenes, Alkynes (# of bonds)? - Correct Answers -Alkanes =>
Hydrocarbons with single-bonded carbons

Alkenes =>
Hydrocarbons with double-bonded carbons

Alkynes =>
Hydrocarbons with triple-bonded carbons

Base Names for Hydrocarbons - Correct Answers -meth = 1
eth = 2
prop = 3
but = 4
pent = 5
hex = 6
hept = 7
oct = 8
non = 9
dec = 10

, The Greenhouse Effect - Correct Answers -Greenhouse gases in the atmosphere act as
a one-way filter.

They allow sunlight to pass through and warm Earth's surface.

Prevent heat energy from radiating back out into space.

Stoichiometry - Correct Answers -The numerical relationships between the amount of
reactants and the amount of products in a balanced chemical equation.

Coefficients in a Chemical Reaction (function) - Correct Answers -The amounts (in
moles) of the reactants and the products in a chemical reaction.

Limiting Reactant (Reagent) - Correct Answers -The reactant that has the smallest
stoichiometric amount in a reactant mixture and hence limits the amount of product in a
chemical reaction.

The reactant that makes the least amount of product.

Completely consumed in a chemical reaction

NOTE:
- Also called "limiting reagent"

Excess Reactant (Reagent) - Correct Answers -The reactants that do not limit the
amount of product (in excess)

Usually greater than what is required to completely react with the limiting reactant.

Theoretical Yield - Correct Answers -The maximum possible amount (in grams) of
product that can be made in a chemical reaction based on the amount of limiting
reactant.

TY = [Amount of product by limiting reactant]
x
[Molar mass of product]

Actual Yield - Correct Answers -The amount of product ACTUALLY produced by a
chemical reaction.

Always equal to or less than the Theoretical Yield because a small mount of product is
usually lost to other reactions or foes not form during a reaction.

Percent Yield - Correct Answers -The percentage of the Theoretical Yield that was
actually obtained.