CHEM 101L STUDY GUIDE QUESTIONS AND ANSWERS
Q1, Density: The volume marking at the sealed bottom of a buret segment is 38.60
mL, and has markings for every 0.1 mL. When water is added, the bottom of the
meniscus sits about halfway between the line for 18.3 mL and the next mark up.
What volume of water is contained in the buret segment?
38.60mL-18.25mL= 20.35mL
Q1, Density: When calculating the displacement volume of the thermometer, the
volume reading on the buret is 28.47 mL without the thermometer, and 27.82 mL
with the thermometer in place. How many significant figures should be recorded
for the displacement volume of the thermometer?
Select one:
28.47mL-27.82mL=0.65mL
2 sig figs!
Q1, Density: Using the graph shown from an experiment measuring the density of
water, what would be the correct value, units, and significance of the intercept of
the regression line?
1.034 g/mL represents the density at a temperature of 0 Celsius.
Q1, Density: A student creates the following graph after an experiment measuring
the density of water. Suppose the thermometer the student used was improperly
calibrated and always read a value 3.5 degrees below the true temperature. Which
of the following statements would be true?
The slope of the regression line would be correct, but the intercept would read a value
that was less than the true value.
Q2, Aqueous Rxns: For the reaction of 3.5 g of sodium bicarbonate with 30 mL of
0.5 M HCl if the temperature rises from 22.4°C to 32.1°C. The value of ΔT/mol
(°C/mol) would be:
233 degrees C/mol
- (9.7 degrees C)/((3.5 g)/(84.007 g/mol))
-NaHCO3 was limiting reactant
Q2, Aqueous Rxns: The molecular equation of a reaction is NaHCO3(aq)+HCl(aq)-
> NaCl(aq)+H2O(l)+CO2(g). Both the initial solutions and the final solution were
transparent and colorless, but bubbles were seen during the reaction. Based on
this equation and the observations of the reaction, the spectator ions in the ionic
equation would be:
2 of the above: Na+(aq) and Cl-(aq)
Q2, Aqueous Rxns: The temperature at the start of a reaction was 22.8 degrees C
and the final temperature was 32.9 degrees C. Based on these observations, the
reaction of the sodium bicarbonate with hydrochloric acid would be:
Exothermic, because energy was transferred from the reaction to the surroundings.
Q2, Aqueous Rxns: 5.224 g in a buret segment with a largest volume increment of
50.00 mL shows a corrected volume of 44.3 mL at a certain temperature. How
many significant figures will be present in the correct representation of the
density?
, -d=m/v
-(5.224 g)/44.3 mL=0.118 g/mL
-3 significant figures
Q2, Aqueous Rxns: A buret segment with a largest volume increment of 35.00 mL
is filled with pure water to approximately halfway between 19.2 and the mark
above it. After adding the probe, the meniscus moves to halfway between 18.9
and the mark just under it. What is the original volume of the water in the buret?,
35.00mL-19.15mL= 15.85 mL
Q5, Gas Forming Rxns and Rockets: The following three actions could produce a
significant source of error in the results for Experiment 5:
-Losing H2 gas because it is much less dense than air.
-Collecting gases while the reaction is still hot, resulting in mostly H2O vapor in
the bulb.
-Leaving moisture on the spark gun tip before firing.
True: all three are examples of random error
Q5, Gas Forming Rxns and Rockets: Two calorimetry trials were performed with
barium hydroxide and ammonium chloride. The first, using 2.0 g of barium
hydroxide with 10 mL of a 0.5 M ammonium chloride solution showed a
temperature change from 23.2 oC to 12.5 oC. The second trial showed a
decreased from 25.7 oC to 20.4 oC after addition another 10 mL of 0.5 M
ammonium chloride to 1.0 g of barium hydroxide in the calorimeter. What does
this observation suggest about the reaction.
The reaction of barium hydroxide and ammonium chloride is endothermic. The energy
absorbed is directly related to the difference in the initial temperature upon mixing the
substances
-temp decreases in both trials: the rxn is endothermic
-energy absorbed is directly related to the moles of the substances reacting (not the
temperature bc temp is just an effect of the rxn occurring)
Q5, Gas Forming Rxns and Rockets: According to the stoichiometry of the
exothermic reaction equation 2 H2(g) + O2(g) →2 H2O(g), the maximum energy
that can be released by this reaction would occur at a H2:O2 ratio of
2:1 (look at reactants' side)
Q5, Gas Forming Rxns and Rockets: The following equations represent reactions
used in Experiment 5. Of these reactions, choose the correctly balanced
oxidation-reduction reaction.
2 HCl (aq) + Zn (s) → H2 (g) + ZnCl2 (aq)
-hints: Zn stands alone and then pairs up with another atom
-it's also balanced correctly while some of the other redox rxns aren't
Q5, Gas Forming Rxns and Rockets: What does CV measure? How do the
numbers correlate?
CV measures precision. The higher the CV, the lower the precision.
Q4, Conductometric titration: The reaction of zinc with hydrlochloric acid seen in
experiment 5 produces hydrogen gas via the equation featured below. Which of
the following species gets reduced?
Zn (s) + 2 HCl (aq) → H2 (g) + ZnCl2 (aq)
Q1, Density: The volume marking at the sealed bottom of a buret segment is 38.60
mL, and has markings for every 0.1 mL. When water is added, the bottom of the
meniscus sits about halfway between the line for 18.3 mL and the next mark up.
What volume of water is contained in the buret segment?
38.60mL-18.25mL= 20.35mL
Q1, Density: When calculating the displacement volume of the thermometer, the
volume reading on the buret is 28.47 mL without the thermometer, and 27.82 mL
with the thermometer in place. How many significant figures should be recorded
for the displacement volume of the thermometer?
Select one:
28.47mL-27.82mL=0.65mL
2 sig figs!
Q1, Density: Using the graph shown from an experiment measuring the density of
water, what would be the correct value, units, and significance of the intercept of
the regression line?
1.034 g/mL represents the density at a temperature of 0 Celsius.
Q1, Density: A student creates the following graph after an experiment measuring
the density of water. Suppose the thermometer the student used was improperly
calibrated and always read a value 3.5 degrees below the true temperature. Which
of the following statements would be true?
The slope of the regression line would be correct, but the intercept would read a value
that was less than the true value.
Q2, Aqueous Rxns: For the reaction of 3.5 g of sodium bicarbonate with 30 mL of
0.5 M HCl if the temperature rises from 22.4°C to 32.1°C. The value of ΔT/mol
(°C/mol) would be:
233 degrees C/mol
- (9.7 degrees C)/((3.5 g)/(84.007 g/mol))
-NaHCO3 was limiting reactant
Q2, Aqueous Rxns: The molecular equation of a reaction is NaHCO3(aq)+HCl(aq)-
> NaCl(aq)+H2O(l)+CO2(g). Both the initial solutions and the final solution were
transparent and colorless, but bubbles were seen during the reaction. Based on
this equation and the observations of the reaction, the spectator ions in the ionic
equation would be:
2 of the above: Na+(aq) and Cl-(aq)
Q2, Aqueous Rxns: The temperature at the start of a reaction was 22.8 degrees C
and the final temperature was 32.9 degrees C. Based on these observations, the
reaction of the sodium bicarbonate with hydrochloric acid would be:
Exothermic, because energy was transferred from the reaction to the surroundings.
Q2, Aqueous Rxns: 5.224 g in a buret segment with a largest volume increment of
50.00 mL shows a corrected volume of 44.3 mL at a certain temperature. How
many significant figures will be present in the correct representation of the
density?
, -d=m/v
-(5.224 g)/44.3 mL=0.118 g/mL
-3 significant figures
Q2, Aqueous Rxns: A buret segment with a largest volume increment of 35.00 mL
is filled with pure water to approximately halfway between 19.2 and the mark
above it. After adding the probe, the meniscus moves to halfway between 18.9
and the mark just under it. What is the original volume of the water in the buret?,
35.00mL-19.15mL= 15.85 mL
Q5, Gas Forming Rxns and Rockets: The following three actions could produce a
significant source of error in the results for Experiment 5:
-Losing H2 gas because it is much less dense than air.
-Collecting gases while the reaction is still hot, resulting in mostly H2O vapor in
the bulb.
-Leaving moisture on the spark gun tip before firing.
True: all three are examples of random error
Q5, Gas Forming Rxns and Rockets: Two calorimetry trials were performed with
barium hydroxide and ammonium chloride. The first, using 2.0 g of barium
hydroxide with 10 mL of a 0.5 M ammonium chloride solution showed a
temperature change from 23.2 oC to 12.5 oC. The second trial showed a
decreased from 25.7 oC to 20.4 oC after addition another 10 mL of 0.5 M
ammonium chloride to 1.0 g of barium hydroxide in the calorimeter. What does
this observation suggest about the reaction.
The reaction of barium hydroxide and ammonium chloride is endothermic. The energy
absorbed is directly related to the difference in the initial temperature upon mixing the
substances
-temp decreases in both trials: the rxn is endothermic
-energy absorbed is directly related to the moles of the substances reacting (not the
temperature bc temp is just an effect of the rxn occurring)
Q5, Gas Forming Rxns and Rockets: According to the stoichiometry of the
exothermic reaction equation 2 H2(g) + O2(g) →2 H2O(g), the maximum energy
that can be released by this reaction would occur at a H2:O2 ratio of
2:1 (look at reactants' side)
Q5, Gas Forming Rxns and Rockets: The following equations represent reactions
used in Experiment 5. Of these reactions, choose the correctly balanced
oxidation-reduction reaction.
2 HCl (aq) + Zn (s) → H2 (g) + ZnCl2 (aq)
-hints: Zn stands alone and then pairs up with another atom
-it's also balanced correctly while some of the other redox rxns aren't
Q5, Gas Forming Rxns and Rockets: What does CV measure? How do the
numbers correlate?
CV measures precision. The higher the CV, the lower the precision.
Q4, Conductometric titration: The reaction of zinc with hydrlochloric acid seen in
experiment 5 produces hydrogen gas via the equation featured below. Which of
the following species gets reduced?
Zn (s) + 2 HCl (aq) → H2 (g) + ZnCl2 (aq)
