CHEM 101L FinaL ExaM QuEstions witH
answErs 100% CorrECt
A small vial of flammable liquid spills and ignites in the hood. Your TA asks you to bring the fire
extinguisher while he moves students back from the hood, so you look for the fire extinguisher
____________________. ✔✔ hanging on the side of a bench near the door
In the experiment described above, the pH after mixing was measured initially as 2.4, then increased and
stabilized at a value of 3.9. A well-reasoned explanation for this result would be: ✔✔ Based solely on the
number of moles added, there should be excess base, and a pH greater than 7. However, because the
solubility of magnesium hydroxide is low, it is possible that not all moles of base were in solution, and a
slowly rising pH could be caused as more base dissolves.
If the balanced equation for the reaction of calcium carbonate with hydrochloric acid is:
2 HCl (aq) + CaCO3 (s) —► CaCl2 (aq) + CO2 (g) + H2O (l)
How many moles of HCl can be neutralized by an antacid containing 750 mg (7.50x102 mg) of calcium
carbonate? (CaCO3 MW = 100.0869 g/mol) ✔✔ 0.0150 mol
A tablet containing 1000 mg calcium carbonate and 300 mg magnesium hydroxide should neutralize
more acid than a tablet containing 1500 mg calcium carbonate alone because __________________.
CaCO3 MW = 100.0869 g/mol
Mg(OH)2 MW = 58.3197 g/mol
CaCO3 + 2 HCl —► CaCl2 + H2O + CO2
Mg(OH)2 + 2 HCl —► MgCl2 + 2 H2O ✔✔ There are more moles of base.
, The molecular equation for the reaction in Experiment 4 is:
Ba(OH)2 + H2SO4 → BaSO4 + 2 H2O
How is conductivity reflected in the net ionic equation? ✔✔ Barium hydroxide is a soluble ionic
substance that is highly conductive in solution, and sulfuric acid is a strong acid that also conducts
strongly in solution. In contrast, barium sulfate is an ionic solid, and, as a solid, it is nonconductive. Water
is a covalent substance that is also a nonconductor. Therefore, the net ionic equation will have no
spectator ions, and only the reactants will be written as ions in solution.
In a conductivity titration, 10.15 mL of 4.95 x 10-3 M Ba(OH)2 is titrated by 12.11 mL of a H2SO4
solution. Given the end point volume of titrant, what is the concentration of the H2SO4 solution? ✔✔
4.15 x 10-3 M
During a conductivity titration, 15.0 mL of Ba(OH)2 is placed in a beaker with 35 mL of H2O. At the start
of the titration, the initial conductivity reading is nearly double that of a previous trial and does not
decrease to zero at the minimum as expected as sulfuric acid is added, even though the minimum occurs
at the expected volume. One possible explanation for these observations would be: ✔✔ Instead of
adding distilled water to the barium hydroxide, the experimenter added tap water.
In the reaction NaOH(s) + HCl (aq) ->NaCl(aq) + H2O(l), the species present in the net ionic equation
would be: ✔✔ NaOH, H2O, Na+, H+
In a calorimetry experiment, 50.0 mL each of two dilute aqueous solutions are combined and produce an
extrapolated delta T = 22.4C̊. If the density of each solution is assumed to be equal to that of water (at
20C̊, d = 0.9982 g/mL), and the specific heat of the solution is also equal to that of water (4.186 J/gC̊),
the value of qrxn would be: ✔✔ -9.36 kJ
Part of the data analysis for Experiment 6 included the calculation of ccal, the calorimeter constant. If
this constant was not known, what effect might it have on the results of the experiment? ✔✔ Any heat
from the reaction that was lost to the calorimeter would not be measured. Therefore the value of qrxn
would appear to be lower than its actual value, and would produce a low value for the enthalpy of the
reaction.
answErs 100% CorrECt
A small vial of flammable liquid spills and ignites in the hood. Your TA asks you to bring the fire
extinguisher while he moves students back from the hood, so you look for the fire extinguisher
____________________. ✔✔ hanging on the side of a bench near the door
In the experiment described above, the pH after mixing was measured initially as 2.4, then increased and
stabilized at a value of 3.9. A well-reasoned explanation for this result would be: ✔✔ Based solely on the
number of moles added, there should be excess base, and a pH greater than 7. However, because the
solubility of magnesium hydroxide is low, it is possible that not all moles of base were in solution, and a
slowly rising pH could be caused as more base dissolves.
If the balanced equation for the reaction of calcium carbonate with hydrochloric acid is:
2 HCl (aq) + CaCO3 (s) —► CaCl2 (aq) + CO2 (g) + H2O (l)
How many moles of HCl can be neutralized by an antacid containing 750 mg (7.50x102 mg) of calcium
carbonate? (CaCO3 MW = 100.0869 g/mol) ✔✔ 0.0150 mol
A tablet containing 1000 mg calcium carbonate and 300 mg magnesium hydroxide should neutralize
more acid than a tablet containing 1500 mg calcium carbonate alone because __________________.
CaCO3 MW = 100.0869 g/mol
Mg(OH)2 MW = 58.3197 g/mol
CaCO3 + 2 HCl —► CaCl2 + H2O + CO2
Mg(OH)2 + 2 HCl —► MgCl2 + 2 H2O ✔✔ There are more moles of base.
, The molecular equation for the reaction in Experiment 4 is:
Ba(OH)2 + H2SO4 → BaSO4 + 2 H2O
How is conductivity reflected in the net ionic equation? ✔✔ Barium hydroxide is a soluble ionic
substance that is highly conductive in solution, and sulfuric acid is a strong acid that also conducts
strongly in solution. In contrast, barium sulfate is an ionic solid, and, as a solid, it is nonconductive. Water
is a covalent substance that is also a nonconductor. Therefore, the net ionic equation will have no
spectator ions, and only the reactants will be written as ions in solution.
In a conductivity titration, 10.15 mL of 4.95 x 10-3 M Ba(OH)2 is titrated by 12.11 mL of a H2SO4
solution. Given the end point volume of titrant, what is the concentration of the H2SO4 solution? ✔✔
4.15 x 10-3 M
During a conductivity titration, 15.0 mL of Ba(OH)2 is placed in a beaker with 35 mL of H2O. At the start
of the titration, the initial conductivity reading is nearly double that of a previous trial and does not
decrease to zero at the minimum as expected as sulfuric acid is added, even though the minimum occurs
at the expected volume. One possible explanation for these observations would be: ✔✔ Instead of
adding distilled water to the barium hydroxide, the experimenter added tap water.
In the reaction NaOH(s) + HCl (aq) ->NaCl(aq) + H2O(l), the species present in the net ionic equation
would be: ✔✔ NaOH, H2O, Na+, H+
In a calorimetry experiment, 50.0 mL each of two dilute aqueous solutions are combined and produce an
extrapolated delta T = 22.4C̊. If the density of each solution is assumed to be equal to that of water (at
20C̊, d = 0.9982 g/mL), and the specific heat of the solution is also equal to that of water (4.186 J/gC̊),
the value of qrxn would be: ✔✔ -9.36 kJ
Part of the data analysis for Experiment 6 included the calculation of ccal, the calorimeter constant. If
this constant was not known, what effect might it have on the results of the experiment? ✔✔ Any heat
from the reaction that was lost to the calorimeter would not be measured. Therefore the value of qrxn
would appear to be lower than its actual value, and would produce a low value for the enthalpy of the
reaction.
