CHEM 1411
Practice Lab Exam: Total 100 points.
Separation of the Components in an Inorganic Mixture
Mass of evaporating dish:
42.8 g
Mass of evaporating dish and unknown mixture:
45.6 g
Mass of unknown mixture:
_________2.8_____ g
Mass of evaporating dish after subliming NH4Cl:
44.6 g
Mass of NH4Cl:
___1.0____________ g
Percent of NH4Cl:
_____35.71________ %
(Show calculations for percent of NH4Cl)
(1.0/2.8)x100%
What does MSDS mean? This is to ask you to write out the whole words of this abbreviation.
Material Safety Data Sheet
Why you must do the first heating in the fume hood?
The white fume has odor and irritant to lung
What chemicals are in the white fume you saw in the experiment?
Hydrogen chloride (HCl) and ammonia (NH3)
What is the major error contributed to percent recovery in this experiment?
Spattering of sand, salt or both
What attributes to the recovery greater than 100% in this experiment?
Sand, salt or both are not dried completely
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The Iron-copper Molar Ratio-Single Replacement Reaction and Limiting Reagent
The quantities of chemical used, copper (II) sulfate pentahydrate and iron metal, are actually in
the stoichiometric quantities, and the data sheet of this experiment is not clear, and thus no
calculation from this experiment will be asked.
What are the color and chemical formula of copper (II) sulfate pentahydrate, respectively?
Blue, CuSO4.5H2O
What does it mean “limiting reactant or limiting reagent”?
The reactant that is used up first or completely during a chemical reaction and thus it
limits the amount for product(s) produced.
What is the major source of error of this experiment?
The replaced Cu metal (molar mass is about 63.55 g/mol) is not washed completely with
de-ionized and dried. If any of copper (II) sulfate pentahydrate (molar mass is about 250
g/mol) remains, the error will be huge.
Reactions in Aqueous Solutions: Single- and Double-Displacement Reactions:
Write its balanced molecular equation and net-ionic equation respectively for zinc metal and
hydrochloric acid.
Molecular: Zn(s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
Net-Ionic: Zn(s) + 2H+ (aq)  Zn2+ (aq) + H2 (g)
Write its balanced molecular equation and net-ionic equation respectively for sodium
carbonate and hydrochloric acid.
Molecular: Na2CO3(aq) + HCl(aq)  2NaCl(aq) + H2O (l) + CO2 (g)
Net-Ionic: CO32- (aq) + 2H+ (aq)  H2O (l) + CO2 (g)
Write its balanced molecular equation and net-ionic equation respectively for calcium chloride
and sodium sulfide.
Molecular: CaCl2(aq) + Na2S(aq)  CaS (s) + 2NaCl (aq)
Net-Ionic: Ca2+ (aq) + S2- (aq)  CaS (s)
Write its balanced molecular equation and net-ionic equation respectively for
nickel (II) chloride and silver nitrate.
Molecular: NiCl2 (aq) + 2AgNO3 (aq)  2AgCl (s) + Ni(NO3)2 (aq)
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Net-Ionic: Ag+ (aq) + Cl- (aq)  AgCl (s)
Write its balanced molecular equation and net-ionic equation respectively for hydrochloric
acid and sodium hydroxide.
Molecular: HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)
Net-Ionic: H+ (aq) + OH- (aq)  H2O (l)
Write its balanced molecular equation and net-ionic equation respectively for potassium
chloride and sodium nitrate.
Molecular: KCl (aq) + NaNO3 (aq)  NaCl (aq) + KNO3 (aq)
Net-Ionic: There is no net ionic equation.
Column Chromatography of Spinach
What kinds of pigments are there in spinach?
Chlorophyll and beta-carotene are the two main kinds.
What does it mean eluent?
The eluent is the "carrier" portion of the mobile phase that coming out from the column. It
moves the analytes through the chromatograph. In liquid chromatography, the eluent is the liquid
solvent; in gas chromatography, it is the carrier gas. Elution is the process of extracting one
material from another by washing with a solvent.
The eluate, or mobile phase is a combination of the mobile phase "carrier" and the
analyte material that emerge from the chromatograph. It specifically includes both the analytes
and solutes passing through the column, while the eluent is only the carrier.
What does it mean UV-Vis spectrophotometer? This is to ask you write out the whole words of
UV-Vis.
Ultraviolet-Visible Spectrophotometer or spectrometer
Why you can only touch the frosted side of the cuvette or have to wipe the cuvette?
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The fingerprints may absorb the light and interfere with the results.
What does it mean “blank”?
A Blank solution is one that does not have any chemical that you are looking for or
measuring or detecting.
A blank solution is a solution containing little to no analyte of interest, usually used to
calibrate instruments such as a colorimeter, UV-Vis spectrometer.
A blank solution is the solution prepared accordingly without analyte in there.
Molar Mass of a Volatile Liquid:
Mass of flask + cap + rubber band
45.6 g
Temperature of boiling water
98 oC
Barometric pressure
745 mm Hg
Mass of flask + rubber band + cap + condensed vapor
45.8 g
Mass of condensed liquid
__0.2_______________ g
Volume of flask
143 mL
Molar mass of vapor
______43.42__________ g/mol
(Show calculations)
PM = dRT ; 1 L= 1000 mL
(745/760) x M = (0.2 / 0.143) x 0.082 x (98 +273.15)  M = 43.42
Why you need to wipe the aluminum foil inside and outside before you weight it after heating?
It may trap water and affects the weighing.
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