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CHEM LAB FINAL EXAM QUESTIONS
AND ANSWERS LATEST UPDATE
GRADED A+ 2023/2024

Which statement is true about a chemical reaction at equilibrium? - ANSWER- The
forward reaction rate is equal to the reverse reaction rate
...
If you create an equilibrium mixture from
Fe3+ and SCN− ions, adding Cl− ions will _____________________ because
______________________________
...
- ANSWER- endothermic

Heat is a product in the reaction - ANSWER- exothermic

When any reversible reaction is at equilibrium, what conditions are necessarily
true? - ANSWER- -Reactants and products are both present in the reaction mixture
...


-The amounts of reactants and products has stopped changing
...
Heat applied to an endothermic
reaction will shift the reaction towards _______________
...
- ANSWER- -titrant volume

-pH

If a 1
...
40 mL of 0
...
36 M
1
...
258 M x (32
...
0083592
2
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0083592x1000

If 0
...
50 mL of 0
...
find moles of base:
(
...
5)/1000=
...
find molar mass of acid:

...
0011475=65

The pKa of an acid can be determined through _____________ with a strong base
...
The pKa of the acid is equal to the pH at the
___________________
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- ANSWER- Cl-=HCl

I-=HI
SO42-=Bisulfate ion
F-=HF
OH-=Water

Given the pKa of each acid, determine whether it is strong or weak
...
1
weak

acetic acid, pKa=4
...
Rinse the pH meter with __________________
and gently pat dry
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- ANSWER- -storage solution

-deionized water
-stabilizes

Would the pH at the equivalence point be acidic, basic, or neutral for each given
titration? - ANSWER- HClO4 with
Ba(OH)
neutral

HCl with NH3
acidic

CH3CH2OH with Sr(OH)2
basic

The equivalence point of any acid-base titration can be determined visually from a
titration curve by finding the place where - ANSWER- the curve has the steepest
slope
...


If the pH at the half-titration point of a weak acid is 4
...
3E-5

10^-4
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0 mL sample of a saturated
Ca(OH)2 solution is titrated with 0
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9 mL of titrant are dispensed
...
019

(
...
9)/1000
HCl is 2x the moles of Ca(OH)2
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0 mL sample of a saturated
Ca(OH)2 solution is titrated with 0
...
5 mL of titrant are dispensed
...
034

Begin by finding the number of moles of the titrant,
HCl
...


(0
...
5)/1000

The molar solubility of
Ca(OH)2 was experimentally determined to be 0
...
Based on this value, what
is the Ksp of Ca(OH)2? - ANSWER- 0
...
022)(2*0
...
This is
because the NaF solution contains __________________ that __________ further
dissociation of PbF2 into Pb2+ and F-
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Any further addition of salt will remain undissolved
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- ANSWER- Solubility product
constant

A decrease in the solubility of an ionic compound as a result of the addition of a
common ion
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ANSWER- Molar solubility
The mass of a salt in grams that will dissolve in 100 mL of water
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25 x 10-5 M Ag+
ions
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- ANSWER- 1
...
25E-5M)(1
...
60 mL
of 0
...
Based on this titration, what is the Ksp of AgOH?
- ANSWER- 2
...
00260 L x 0
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54E-5/
...
41E-4
(1
...
00E-8

Consider the equilibrium describing the endothermic dissolution of a solid in
water
...

Suppose you add 0
...
0 mL of water
...
0159 M and the concentration of Cl−(aq)) is
0
...
What is the value of the equilibrium constant, Kc, for the dissolution of
PbCl2? - ANSWER- 1
...
0159 M][0
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ANSWER- -A: 0
...
At the beginning of the titration, you read the base titrant volume as 2
...

After running the titration and reaching the endpoint, you read the base titrant
volume as 18
...

What volume, in mL, of base was required for the titration? - ANSWER- 16
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- ANSWER- -Close to
the calculated endpoint of a titration: Partially open

-Filling the buret with titrant: completely closed

-at the beginning of aa titration: completely open

-Conditioning the buret with titrant: completely closed

A reagent added to the analyte solution that changes color when the reaction is
complete - ANSWER- Indicator

Solution of an unknown concentration that has another solution slowly added to it ANSWER- Analyte

Glassware that allows a solution to be precisely and slowly added to another
solution - ANSWER- Buret

Solution of known concentration that is slowly added to a solution of unknown
concentration - ANSWER- Titrant

Process of slowly adding a solution to react with another solution and determine
the concentration of one of the solutions based on the reaction between them ANSWER- Titration

When the required amount of one solution has been added to the second solution to
complete the reaction - ANSWER- Endpoint
How should you prepare a buret for titration before loading it with titrant? ANSWER- Condition the buret with titrant solution

Suppose you analyze a 33
...
08 g
of sodium hypochlorite present
...
14

2
...
9 x 100%

Suppose in an experiment to determine the amount of sodium hypochlorite in
bleach,
0
...
63 mL1
...
00644

mols thiosulfate= moles KIO3x6
=9
...
01463) =
...
45 mL sample of 0
...
The endpoint was observed to occur at 14
...


How many moles of
KIO3 were titrated? - ANSWER-
...
0100molx
...
0000443 mol KIO3 were titrated with an unknown solution of Na2S2O3 and the
endpoint was reached after 17
...


How many moles of
Na2S2O3 did this require? - ANSWER-
...
0000443x6

When determining the amount of an oxidant present by titration, you can use
iodine and starch as an indicator
...
When starch
and iodine are both present, the solution is ____________
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When the
iodine has completely reacted at the endpoint of the titration, the solution should
become __________
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- ANSWER- -water
-carbon dioxide
Identify the safety equipment designed to deal with each emergency listed
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29 g of a fuel causes the water in a calorimeter to increase by 11
...
If
the calorimeter has a heat capacity of 3
...
8

-3
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2=-34
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608/1
...
8

Suppose you need to calibrate a calorimeter
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736 g of a fuel with an enthalpy of combustion of −48
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If the temperature
of water in the calorimeter increases by 14
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47

-48
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736g=-35
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84/14
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47=2
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The calorimeter is __________ to prevent transfer of heat to outside the device
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3 kJ/g and fuel B has an energy density of −35
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The fuel with greater energy density is_________ because you need to burn
_______ of Fuel A than Fuel B to produce the same amount of heat
...

-Inform the instructor and everyone working around the area about the spill
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- ANSWER- -The burner should be lit for 20
seconds after any change before proceeding
...

-The burner wick should be about a few millimeters above the metal stem
...

C7H16+ 11O2-----> 7CO2+ 8H2O
Using the given enthalpies of formation, ΔH∘f for each species, determine the
enthalpy of combustion of heptane
...

EoCell= 1
...
120 M solution of
Zn2+(aq) and 0
...
6 K? - ANSWER- 1
...
1032V-(8
...
6K)/(2x95485)xln(2
...
1550)

Consider the diagram of the electrochemical cell
...
The purpose of the
Na2SO4 is to ____________________
...
In the salt bridge, _________ move toward the anode and
_________ move toward the cathode
...
- ANSWER- Pressure of
1 atm
solution concentrations of 1 M
Temperature of 298 K

what is the standard cell potential - ANSWER- 1
...
36-(-
...
314 J/molK
temperature in K
number of electrons
Faraday constant
reaction quotient

The electrode where oxidation occurs

An electrochemical cell powered by a spontaneous redox reaction

An electrochemical cell that takes in energy to carry out a nonspontaneous redox
reaction

The electrode where reduction occurs

A chemical equation showing either oxidation or reduction - ANSWER- anode

galvanic cell

electrolytic cell

cathode

half-reaction

Identify the oxidation half reaction of Zn(s)
...
- ANSWER2Fe(s) + 3Cl2(g)→ 2Fe3+(aq) + 6Cl-(aq)

Al---->Al3+
Cu2+----> Cu+
2F- ----> F2 - ANSWER- oxidation, 3, product
reduction, 1, reactant
oxidation, 2, product

suppose you mix an unknown solid with oil and the added solid dissolves into the
oil
...
What is most likely true
about the unknown liquid? - ANSWER- It is a polar liquid

Determine whether the structure is correct and justify your decision - ANSWERThis solution is incorrect because the octet rule in not fulfilled
...
o-c-o

what characteristics of molecule determine whether or not it is polar? - ANSWERThe arrangement of bonds around the molecule
...


Determine whether the structure is correct and justify your decision
...
o has 2
lone pairs and 2 bonded pairs
...
ANSWER- c+o2=co2 (combustion)
CO2+4H2=CH4+2H20 (not combustion)
2NO+O2=2NO2 (combustion)
2N2O5=4NO2+O2 (not combustion)
2C2H6+7O2=4CO2+6H20 (combustion)

Determine each type of reaction - ANSWER2C2H2(G)+5O2(G)=4CO2(G)+2H2O(l): COMBUSTION

Determine each type of reaction - ANSWERCACL2(AQ)+NA2CO3(AQ)=2NACL(AQ)+CACO3(S): DOUBLE
REPLACEMENT
Determine each type of reaction - ANSWER2FE(S)+6HCL(AQ)=2FECL3(AQ)+3H2(G): SINGLE REPLACEMENT

Determine each type of reaction - ANSWER- CO(G)+2H2(G)=CH3OH(L) :
COMBINATION

Determine each type of reaction - ANSWER- NH4NO3(S)=N2O(G)+2H2O(L):
DECOMPOSITION
In the context of a balanced chemical equation, a - ANSWER- (subscript) is a
number to the lower right of an element or ion within formula and it applies to
(only the part of the formula it follows)
...
Only (coefficients) should
be added or changed when balancing chemical equations
...
At least
one reactant
...


Determine what type of reaction each unbalanced chemical equation represents
...
ANSWER- AgNO3+NaCl=NaNO3+AgCl (double replacement)

Determine what type of reaction each unbalanced chemical equation represents
...
ANSWER- CaCL2+Na3PO4=Ca3(PO4)2+NaCl (double replacement)

predict the products of hydrochloric acid reacting with zinc metal
...
- ANSWER- Capable of measuring a range of volumes of
liquid (graduated)

Determine whether each of the properties described applies to volumetric or
graduated glassware
...
First, you test
a potassium compound, which appears violet
...
However, you do not see the correct flame
color
...

Incorrect appearance 1: The flame appears weakly yellow
...
Compare to a known sodium compound to
distinguish
...
- ANSWER- There is not enough
solution on the wire
...


Incorrect appearance 3: The flame appears violet
...
Clean with acid and try again
...
Solid settling out in the test tube

Identify some of the cations that will be detected in the procedure Qualitative
Analysis of Some Cations and Anions
...
- ANSWER- Formation of a red-brown
precipitate of Cu2[Fe(CN)6]

occurs when aqueous ammonia is added to a solution containing Bi3+ and Cu2+
ions
...

Cu+2AgNO3= Cu(NO3)2+2Ag - ANSWER- Kc= [Cu(NO3)2]/[AgNO3]2

Fill in the expression for the equilibrium constant Kc for the reaction given
...


Heat is a reactant in the reaction - ANSWER- endo
The reaction mixture feels warm from the outside - ANSWER- exo

The reaction mixture feels cool from the outside - ANSWER- endo

Heat is a product in the reaction - ANSWER- exo

When any reversible reaction is at equilibrium, what conditions are necessarily
true? - ANSWER- Reactants and products are both present in the reaction
mixture
...
The rate of
the forward reaction equals the rate of the reverse reaction
...
95

A saturated solution of lead iodine, PbI2 has an iodide concentration of 3
...
What is the molar solubility of PbI2? (quiz 9) - ANSWER- PbI2 = Pb 2+ + 2
I- =
3
...
5 x 10-3

part b
...
5x10-3)(0
...
35x10-8
What is the indicator used to detect the endpoint in the titration for this
experiment? (quiz 9) - ANSWER- methyl orange indicator

What is the expected color change at the endpoint in this experiment (quiz 9) ANSWER- yellow to a faint red-or

Muriatic acid is used to adjust the pH of swimming
...
(quiz 8) - ANSWER- HCl is the formula
...


Battery acid is a rather concentrated solution of sulfuric acid
...
What is the
formula of milk of magnesia? (quiz 8) - ANSWER- Mg(OH)2

Washing soda is often added to detergent formulations to make the wash water
more basic
...
(quiz 8) - ANSWER- Na2CO3
...


ph solutions (quiz 8) - ANSWER- most acidic concentration = highest h3o ion
concentration
lowest ph = most acidic
highest ph = most basic

Identify the reagent (and concentration) that is used to confirm the presence of
each of the following (quiz 6) - ANSWER- Ni2+ = dimethylglyoxime
fe3+ =
Zn2+ = 0
...
Explain the chemistry of the
separation
...
Fe3+ + 3 NH3 + 3 H2O yields Fe(OH)3 + 3
NH4 + Ni2+ + 6 NH3 yields [Ni(NH3)6]2+

identify the reagent that separates fe3+ from zn2+
...
Zincate gets dissolved in solution
...
Zn 2+ forms soluble complex

In the collection of the rate data for the experiment, when do START TIME and
STOP TIME occur for each kinetic trial? (quiz 3) - ANSWER- The start time
occurs when solution A and B have combined
...


What is the color of the solutions at stop time? (quiz 3) - ANSWER- The color of
the solution at stop time is a deep blue black color

in kinetic analysis of this experiment for the reaction of iodine ion with hydrogen
peroxide, state the purpose for each of the following solutions
...


In some solid calcium carbonate samples, calcium bicarbonate is also present
...
(quiz 1) ANSWER- Ca(HCO3)2 + 2 HCl (aq) yields CaCl2 + 2 H2O + 2CO2 (g)

A thermometer is not present in the space in which the CO2 (g) is collected in this
experiment
...
How then is the temperature of the CO2 (g) determined in this
experiment? B
...
How is the mass of the CO2(g)
collected over water determined in this experiment? (quiz 1) - ANSWER- a
...

b
...


Write a balanced equation for the reaction of the active ingredient in Tums with
excess acid
...
(quiz 5) - ANSWERHydroxide: OH- and Carbonate: CO3^2-

How much time should be allowed for the titrant to drain from the buret wall
before a reading is made? (quiz 5) - ANSWER- 10-15 seconds

how many moles of stomach acid would be neutralized by one tablet of Tums 1000
that contains 1000 mg of calcium carbonate?

CaCO3 (aq) + 2 H3O+ (aq) yields Ca 2+ (aq) + CO2 (g) + 3 H2O (l) - ANSWER1) 1000 mg = 1g , molar mass of CaCO3 = 100 g/mol

CaCO3 moles = mass of CaCO3 in grams / Molar mass of CaCO3 = ( 1 g / 100
...
00992

acid moles neutralised = 2 x CaCO3 moles ( from baalanced equation coefficients)
= 2 x 0
...
01984

a 3
...
001 M NaSCN is diluted to 25
...
2 M Fe(NO3)3
and 0
...

A
...
If all of the SCN- is complexed with Fe+ to form FeNCS+,what is the molar
concentration of FeNCS+? (quiz 4) - ANSWER- A
...
001 x 0
...
0 x 10-6
B
...
0 x 10-6/25 ml = 1
...
(titrations) ANSWER- Analyte

When equal moles of an acid and a base are mixed, after reaction the two are
compounds are said to be at the _______________
...
ANSWER- NaCl(aq) + H2O(l)

Acid Base Neutralization reactions for H2O and a salt

The liquid dispensed from a burette is called ___________
...


Potassium hydrogen phthalate is ____________
...
- ANSWER- A titration

Which term describes a solution having a very well-known concentration of
solute? - ANSWER- Standard Solution

The standard solution is a solution of known concentration that can be used to
titrate a solution of unknown concentration
...
their concentrations, what
is the slope equal to? - ANSWER- Molar absorptivity, if the path length is 1 cm

What is the concentration (in M) of a sample of the unknown dye with an
absorbance of 0
...
018 - ANSWER- 0
...
018
x(concentration)=1
...

Suppose one prepares a solution by dissolving 0
...
0 mL solution
...
00 mm
pathlength cell? - ANSWER- Absorbance = molar absorbtivity * path length (cm)
* concentration

Concentration = moles/volume

0

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