CHEM 150 Chapter Notes - Chapter 1-2: Significant Figures, Decimal Mark, Unified Atomic Mass Unit
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n this exercise, weighed samples of a solid unknown containing NaCl and NaHCO3 react with hydrochloric acid. The volume of the CO2 liberated by the reaction in the gas phase is measured with a gas collection syringe. From the volume we can calculate the number of moles of CO2 in the gas phase using the ideal gas approximation.
Since the CO2 is generated in an aqueous environment (aqueous HCl), some CO2 will dissolve in the liquid phase. The amount of CO2 dissolved in the liquid phase is computed using Henry's Law which requires knowing the partial pressure of CO2. As described in the exercise, this requires knowing the volume of the entire gas system ( VfTOT)
To insure that your answers agree with Mr. OSCER's, use the values in the below table for the basic constants required. .
| Value | Units | |
| Ideal Gas Constant | 0.0821 | L-atm/mol K |
| Convert Celsius temperture to Kelvin | 273.15 | K |
| Atmospheric Pressure | 760.0 | Torr |
| Molar Mass of NaHCO3 | 84.01 | g/mol |
| Henry's Law Constant for CO2 in water | 3.2 X 10-2 | mmol/mL-atm |
The figure below illustrates the volumes that are designated by Vtube and Vsyr .
Note also that Vsyr = Vf â Vi .
The table below contains data collected for one run of the required reaction, where an unknown sample mixture containing some NaHCO3 is mixed with hydrochloric acid:
| Value | Units | |
| Initial Weight of container (empty) | 18.4395 | g |
| Final Weight of container and unknown | 18.6185 | g |
| Volume of hydrochloric acid | 10.0 | mL |
| Volume of tube, Vtube (see Figure above) | 92.3 | mL |
| Initial volume of syringe (Vi) | 5.0 | mL |
| Final volume of syringe (Vf) | 50.7 | mL |
| Temperature | 26.5 | oC |
| Atmospheric Pressure | 764.4 | Torr |
| Vapor Pressure of Water at 26.5 oC | 25.8 | Torr |
Use this data to answer the following questions. The appropriate units are specified in the each question. Pay close attention to the number of significant figures in your answers.
weight of sample (g) mixture before the start of the reaction = .179 g. Volume of CO2 gas (mL) that is produced by the reaction and is now contained in the syringe= 45.7 mL
1.
What mass (g) of NaHCO3 was contained in the sample mixture that was mixed with HCl ?
Enter a numeric answer only, to the correct number of significant figures. Do not include units with your answer.
n this exercise, weighed samples of a solid unknown containing NaCl and NaHCO3 react with hydrochloric acid. The volume of the CO2 liberated by the reaction in the gas phase is measured with a gas collection syringe. From the volume we can calculate the number of moles of CO2 in the gas phase using the ideal gas approximation.
Since the CO2 is generated in an aqueous environment (aqueous HCl), some CO2 will dissolve in the liquid phase. The amount of CO2 dissolved in the liquid phase is computed using Henry's Law which requires knowing the partial pressure of CO2. As described in the exercise, this requires knowing the volume of the entire gas system ( VfTOT)
To insure that your answers agree with Mr. OSCER's, use the values in the below table for the basic constants required. .
| Value | Units | |
| Ideal Gas Constant | 0.0821 | L-atm/mol K |
| Convert Celsius temperture to Kelvin | 273.15 | K |
| Atmospheric Pressure | 760.0 | Torr |
| Molar Mass of NaHCO3 | 84.01 | g/mol |
| Henry's Law Constant for CO2 in water | 3.2 X 10-2 | mmol/mL-atm |
The figure below illustrates the volumes that are designated by Vtube and Vsyr .
Note also that Vsyr = Vf â Vi .
The table below contains data collected for one run of the required reaction, where an unknown sample mixture containing some NaHCO3 is mixed with hydrochloric acid:
| Value | Units | |
| Initial Weight of container (empty) | 18.4395 | g |
| Final Weight of container and unknown | 18.6185 | g |
| Volume of hydrochloric acid | 10.0 | mL |
| Volume of tube, Vtube (see Figure above) | 92.3 | mL |
| Initial volume of syringe (Vi) | 5.0 | mL |
| Final volume of syringe (Vf) | 50.7 | mL |
| Temperature | 26.5 | oC |
| Atmospheric Pressure | 764.4 | Torr |
| Vapor Pressure of Water at 26.5 oC | 25.8 | Torr |
Use this data to answer the following questions. The appropriate units are specified in the each question. Pay close attention to the number of significant figures in your answers.
weight of sample (g) mixture before the start of the reaction = .179 g. Volume of CO2 gas (mL) that is produced by the reaction and is now contained in the syringe= 45.7 mL
1.
What is the mass percent of NaHCO3 in the mixture sample ?
Enter a numeric answer only, to the correct number of significant figures. Do not include units with your answer.
In this exercise, weighed samples of a solid unknown containing NaCl and NaHCO3react with hydrochloric acid. The volume of the CO2 liberated by the reaction in the gas phase is measured with a gas collection syringe. From the volume we can calculate the number of moles of CO2 in the gas phase using the ideal gas approximation.
Since the CO2 is generated in an aqueous environment (aqueous HCl), some CO2will dissolve in the liquid phase. The amount of CO2 dissolved in the liquid phase is computed using Henry's Law which requires knowing the partial pressure of CO2. As described in the exercise, this requires knowing the entire system gas volume in addition to the initial and final syringe readings.
The entire system gas volume is the sum of the quantities labeled Vtube and Vsyr in the diagram below, corrected for the liquid volume (the aqueous HCl).
| Value | Units | |
| Gas Constant | 0.0821 | L-atm/mol K |
| Absolute Zero (0 K) | -273.15 | oC |
| Atmosphere | 760.0 | Torr |
| Molar Mass of NaHCO3 | 84.01 | g/mol |
| Henry's Law Constant for CO2in water | 3.2 X 10-2 | mol/L-atm |
The table below contains the data collected in one run of the reaction between an unknown and hydrochloric acid:
| Value | Units | |
| Initial Weight of container and unknown | 18.4395 | g |
| Final Weight of container and unknown | 18.6185 | g |
| Volume of hydrochloric acid | 10.0 | mL |
| Volume of tube, Vtube (see Figure above) | 92.3 | mL |
| Initial volume of syringe | 5.0 | mL |
| Final volume of syringe | 50.7 | mL |
| Temperature | 26.5 | oC |
| Pressure | 764.4 | Torr |
| Vapor Pressure of Water at 26.5 oC | 25.8 | Torr |
The following questions deal with the above data. The appropriate units are specified in the questions. Pay close attention to the number of significant figures in your answers.
1). What is the volume of CO2 captured in the gas phase (in mL)?
2).What is the number of mmols of CO2 captured in the gas phase? (Remember to account for the vapor pressure of water.)
3). What is the weight of the sample in grams?