1. No category

General Chemistry Sample Exam 2 and Outline
Chapter 4 Stoichiometry Calc. & formulas
1 Chemical Equation
Type of Reactions
2 Atomic and Molc' Wt
AW, MW, FW
% Composition
3 The mole
4 Empirical Formula determination
Mol. Formula determination
From Combustion Analysis
5 Stoichiometry problems:
Molecules to moles
Mass to moles
Volume to moles
Using the balance equation, molesa to molesb
Chapter 5
Gaseous State
1
Units of Pressure
2 Ideal Gas Law
Boyle's Law
Charles Law
Avogadro's Law
Combined Gas Law
3 Molar mass by PV=nRT
M = m/n = (m•RT)/PV
4 Dalton's Law of Partial Pressure
PT=Pa + Pb + ...
6 Quantitative Information
Calculating Limiting reagents
Determining the amount of excess
% yield calculations
7 Solution Composition
Concentrations and Molarity
Dilution Calculation
8 Properties of Solution
Aqueous solution (Water)
Ions in Water
Molecules in Water
Electrolytes: Weak electrolytes: nonelectrolytes
9 Acid / Base
Titration calculations and concepts
The experimental setup
Acid-Base Stoichiometry
10 Ionic Equations
11. Metathesis Reaction
Ppt reaction and solubility table
12 Oxidation – Reduction
Electron transfer through single displacement
Activity Series
5
6
Collecting gas over water
Stoichiometry and Gas Laws
Kinetic Molecular Theory
KE=1/2 mu2
7
urms = (3RT / M)1/2
Maxwell-Boltzmann Distribution profile
Diffusion (mixing of gas)
Effusion (passage of gas through hole)
Real gas
Van der Waal equation
8
Conversion information:
System
LENGTH:
English:
1 ft = 12 in
1 mile = 5280 ft
SIEnglish:
2.54 cm = 1 in
1.609 km = 1 mi
Misc. info
VOLUME
1 gal = 4 qt
1 qt = 2 pints
1 pt = 16 fl oz
0.946 L = 1 qt
3.785 L= 1 gal
29.57 mL = 1 fl oz.
1 mole = 6.02•1023
MASS
Temperature
1 lb = 16 oz
1 ton = 2000 lb
T o F = 1.8T o C + 32
453.6 g = 1 lb
28.35 g = 1 oz
1 kg = 2.205 lb
T oC =
(T o F ! 32)
1.8
Density H2O: 1.0 g / cc
General Solubility Table:
Soluble substances
containing nitrates, (NO3-)
chlorate (ClO3-)
Insoluble substances
containing -
Exceptions
carbonate (CO32-)
Phosphate (PO43-)
chromate (CrO42-)
Sulfides (S2-)
None
perchlorate (ClO4-)
Acetate (CH3COO-)
Halogens (X-)
X- = Cl-, Br-, I-
Ag, Hg, Pb
Sulfates (SO42-)
Ca, Ba, Hg, Pb
Alkali & NH4+
slightly soluble
Hydroxides (OH-)
Ca*, Sr, Ba, Alkali, NH4+
* marginally soluble
None
Soluble - dissolve, no precipitate (aq -phase)
insoluble (or slightly soluble) - does not dissolve, precipitate forms. (s-phase)
Gas law equations:
PV = nRT
Ideal Gas Law
Real Gas: vander Waal Equation
Denstiy(D) =
#
a " n2 &
%%P +
(((V - n " b) = nRT
V2 '
$
m " P
, m = mass
n RT
P = 1 atm, T = 0°C, 1 mole = 22.4 L
!
Dalton's Law of Partial Pressure
PT = Pa + Pb + Pc + ...
Pa =
χ
a • PT
Pb =
χ
PT =
b • PT
1
3RT
!
KE = mu2
urms =
2
M
ratea timeb
Mb
=
=
rateb timea
Ma
Speed of Gas particles
Graham's Law of effusion
!
qp =
R = 0.08206
L " atm
mol " K
!
!
STP
Calorimetry
Exceptions
.
χ
(na + n b + n c + ...)R • T .
VT
a = na / nT
J
R = 8.314
mol " K
χ
b = nb / nT
!
!
ΔH = m Cs ΔT where ΔT = Tf - Ti, Cs (H2O) = 4.184 J/g•K
!
_________________________________________________________________________________________________________
1
Combustion of a sulfide of bismuth compound, BixSy (50.00g) in O2 produced 45.30 g of dibismuth trioxide (Bi2O3).
i) What are the IUPAC compound name, empirical formula and the formula weight of the bismuth sulfide (BixSy)
compound?
ii) What is the oxidation state of the sulfur and the bismuth in this compound?
iii) Suppose in your combustion experiment, the BixSy compound also contained some bismuth oxide impurities, how
would this affect the x-value in the empirical formula of BixSy (higher or lower and state your reason)?
iv) Suppose instead of producing 45.30 g dibismuth trioxide in the final product of the combustion, 45.30 g of
dibismuth pentaoxide is produced instead, how would this affect the y-value in the empirical formula of BixSy ?
2
Balance the following equations.
i)
___KOH(aq) + ___H2SO4(aq) → ___ K2SO4(aq) + ___H2O (aq)
ii)
___C4H14(l) + ____O2(g) → ___CO2(g) + ____ H2O(l)
iii)
N2H4(l) + ___O2(g) → ___ NO2 (g) + ___ H2O (g)
iv)
___K2CO3 (aq) + ___H3PO4(aq) → ___ K3PO4 (aq) + ___CO2(g) + ____ H2O(l)
v)
Arsenic(III)oxide + Hydrochloric acid → Arsenic(III)chloride + Dihydrogen monoxide
vi)
Phosphorus + Bromine → Phosphorus tribromide
vii)
Calcium carbonate decomposes to calcium oxide and carbon dioxide
viii)
Copper(II)sulfate pentahydrate is dehydrated to ______ + ______
Identify the type of reaction above.
3
A compound of Ca, C, N, and S was subjected to quantitative analysis and formula mass determination, and the following
data were obtained. A 0.250 g sample was mixed with Na2CO3 to convert all of the Ca to 0.160 g of CaCO3. A 0.0268
g sample of the compound was carried through a series of reactions until all of the S was changed to 0.0802 g of
BaSO4. A 0.712g sample was processed to liberate all of its N as NH3, and 0.155 g NH3 was obtained. The formula
mass was found to be 156 g/mol. Determine the empirical and molecular formulas of this compound.
4
2,4,6-Trinitrotoluene (TNT), C7H5N3O6 , can be prepared by the following two step synthesis:
C6H6 + CH4 → C7H8 + H2
2 C7H8 + 6 NO2 → 2 C7H5N3O6 + 3 H2
If each step in this synthesis gives a 50% yield, how much C7H5N3O6 (TNT) in grams can be produced starting with
780 g of benzene (C6H6) ?
5
Ethyl alcohol (booze), C2H5OH, also called grain alcohol, can be made by the fermentation of glucose, C6H12O6, which
often comes from starch in grain:
___ C6H12O6(aq) → ___ C2H5OH(l) + ___ 2CO2(g)
Determine the maximum mass (theoretical yield) of ethyl alcohol, which could be produced, from 750 g of glucose. If
150 L of CO2 is collected after the fermentation, what is the % yield. Density of CO2 (g) is 1.96 g/ L.
6
Determine which of the following will dissolve in water, then classify these as
(s) strong electrolyte, (w) weak electrolyte or (n) non-electrolyte.
i) NH3
ii) PbSO4
iii) KHSO4
iv) Hg2Cl2
v) HNO3
vi) NH4OH
vii) C2H5OH
Explain your answer
7
Write the net ionic equation for any reaction that occurs upon mixing each pair of solution:
i) silver nitrate and barium chloride
ii) Magnesium sulfate and barium hydroxide
iii) Hydrochloric acid and strontium hydroxide.
iv) Iron(III) sulfide and nitric acid
8
In each of the following reaction, indicate which metal ion is the stronger oxidizing agent, that is rank each metal Zn,
Ag and Pb in order of ease of oxidation . (i.e., Most easily oxidized > next easily oxidize > most difficult to oxidize)
i) Zn (s) + 2AgNO3 (aq) → 2 Ag (s) + Zn(NO3)2 (aq)
ii) Pb (s) + 2AgNO3 (aq) → 2 Ag (s) + Pb(NO3)2 (aq)
iii) Pb (s) + Zn(NO3)2 (aq) → NR.
9
Some sulfuric acid is spilled on a lab bench. Sprinkling some sodium bicarbonate on to the sulfuric acid can neutralize
it. The reaction produces sodium sulfate, carbon dioxide and water.
i) Write the molecular, ionic and net ionic equation and balance the equation (include the phases).
ii) What is the limiting reagent and how much remains if 35 ml of 6.0 M sulfuric acid is spilled and 50 grams of sodium
bicarbonate is added ?
iii) What is the mass of carbon dioxide gas (g) that is produced ?
iv) How many molecules of carbon dioxide are produced ?
v) If 5.00 ml of water is actually produce, what is the % yield of water ?
vi) How many oxygen atoms are involved in this reaction ?
vii) If all the liquid is evaporated, what is the mass of sodium sulfate that is produced ?
viii) What is the concentration of sodium sulfate if 20.0 g sodium sulfate is dissolved in the 5.00 ml water?
10
Consider 100 formula units (or molecules) of each:
a) Tin(IV) hypoiodite
b) carbon tetraiodide
c) cadmium iodite
i) Which compound contains the largest mass of iodine? How much is this mass in grams?
ii) Which contains the greatest mass of metal atoms? For a 100 unit sample, what is the total of these metal atoms ?
iii) If all three of these substances were mixed and added to water, calculate the total number of ions in solution.
11
Balance the following equations and then answer the questions below.
Potassium permanganate is added to hydrochloric acid to produce
chlorine gas, potassium chloride, manganese(II) chloride and water.
i) How many moles of hydrochloric acid are required to react with 45 grams of potassium permanganate ?
ii) How many chlorine molecules will be produced using 5.0 moles of potassium permanganate ?
iii) To produce 55.0 grams of manganese(II) chloride, what mass of hydrochloric acid is required?
iv) How many moles of water will be produce when 7.00 moles of potassium permanganate is consumed ?
v) What is the maximum weight of chlorine that can be produced by reacting 35.0 g of potassium permanganate with
45.0 g of hydrochloric acid ?
vi) In v (above), if the %yield of chlorine in the reaction is 76%, how much (g) chlorine was actually recovered ?
12
Oxygen gas (2.00 mol) is introduce into a 44.8 L rigid container at 1.0 atm and 25°C. What amount of oxygen (in moles)
is necessary to increase the temperature to 50°C if the pressure remains constant.
13
An analysis of a gas yielded an empirical formula of CH2F. If the rate of effusion for Helium is 4.06 times as fast as
this gas,
14
rHe
rCH 2F
= 4.06, what is the molecular formula of this chlorofluorocarbons.
Hydrogen can be prepared in the laboratory by the reaction of zinc and hydrochloric acid. The reaction is :
Zn(s) + 2HCl(aq) --> ZnCl2(aq) + H2(g).
If 44.8 L of H2 is produce from the reaction, how much zinc was used,
assume excess acid and STP conditions P = 1.0 atm, and T = 0°C.
15
Nitric oxide (NO) reacts with molecular oxygen as follows:
2NO (g) + O2(g) →
2NO2(g)
Initially NO and O2 are separated as shown below. When the valve is
NO
4.00 L
0.500 atm
O2
2.00 L
1.00 atm
opened, the reaction quickly goes to completion. Determine what gases
remain at the end and calculate their partial pressure. Assume that the
temperature remains constant at 25° C.
16
For each of the following pairs determine which gas has the largest Urms. Explain your reasoning.
a) Ne (g) or N2 (g) at room temperature
b) H2O (g) at 500°C, or NH3 (g) at 600 K
c) CH4 (g) at 212 °F or NO2 (g) both at 373 K
17
Below are statements that may or may not explain how a hot air balloon rises when the air in the balloon is heated. If
the statement is true, explain why it is consistent with the kinetic molecular theory, if the statement is not true,
rewrite the statement such that it is consistent with the kinetic molecular theory.
a) The average kinetic energy of the molecules increases and the collisions between the molecules and the walls of the
balloon make it rise.
b) The pressure of the gas inside the balloon increases, pushing up on the balloon.
c) The gas expands, forcing some of tit to escape from the bottom of the balloon, and the decrease in the density of
this gas lifts the balloon.
d) The balloon expands, causing it to rise.
e) The hot air rising inside the balloon produces enough force to lift the balloon.
18
The Kinetic molecular theory is a model, which tries to explain the behavior of gases at the molecular level. In the end
though, it is just that, a model, and as such it breaks down under certain conditions and must be modified.
In this essay,
(a) discuss the KMT and how it can be used to explain the following:
(i) why pressure increases with an increase in temperature at constant volume.
(ii) why the Urms for a gas increases with temperature.
(iii) why gases fill their container and why gases are compressible but solids and liquids are not.
Then discuss how this model breaks down under certain conditions, and what corrections must be applied.
(b) What two assumptions of the Kinetic molecular theory becomes invalid, and under what conditions does this occur?
(c) How is the ideal gas law modified in order to account for these inconsistencies.