Chem142 Molar Mass Report Gradescope 051720 with textboxes-converted PDF

Preview

Summary

Download Chem142 Molar Mass Report Gradescope 051720 with textboxes-converted PDF

Description

NAME

Noah Stegman

Quiz Section DP

Student ID# 2072397

CHEM 142 Experiment #6: Molar Mass of a Low Boiling Liquid Goals of this lab: • Apply the ideal gas law to calculate the molar mass of an unknown liquid • Accurately measure quantities (masses, temperature, pressure) in the lab • Evaluate data to determine the identity of an unknown liquid Your lab report will be grade on the following criteria using a poor/good/excellent rating system (see the Lab 6 Self-Assessment on the “Reporting Your Results for Exp #6” page of the lab website for more details): • Calculations are accurate and complete based on data gathered; proper significant figures and units are used • Data collected is reasonable; measurements are careful and accurate • Conclusions are reasonable and logical • Lab report is completed neatly with organized responses and legible handwriting.

By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration will result in 5 points being deducted from your lab score.

Signature:

Noah Stegman

This lab is worth 60 points: 10 points for notebook pages, 50 points for the lab report. (Do NOT include your notebook pages when you scan your report for upload into Gradescope.)

1

NAME

Noah Stegman

Student ID# 2072397

Quiz Section DP

NEATLY show your work. Use a reasonable number of significant figures, include units with your data, and keep your answers concise.

Data from Lab Unknown #: __2____

Run #1

Mass of flask + cap + air:

73.608

Mass of flask + cap + vapor:

73.592

Run #2

Run #3

--

--

73.594

Barometric pressure

73.596

769mmHg

1.01184 atm

Air temperature (for calc. mass of air)

20.5°C

293.65K

Sample temperature (for calc. moles)

100°C

373.15K

Water temperature (for filling flask)

20.4°C

293.55K

Mass of flask + cap + water

185.66g

Density of water at room temperature

0.99820g/mL

Calculations and Results 1) Calculate the volume (in L) of the gas density flask. Neatly show your work. V= (mass of flask + cap + water ) – (mass of flask cap + air)(1/density of water) =(185.66-73.608)(1/.99820) =112.254 mL =0.11225 L

Calculation summary: What is the volume of the flask?

2

0.11225 L

NAME

Noah Stegman

Quiz Section DP

Student ID# 2072397

2) In the following table, copy the required values from the data summary at the top of page 2: Barometric Pressure (atm)

1.01184

Air Temperature (K)

293.65

Calculate the density (in g/L) of air at the temperature and pressure of the laboratory. Assume air is 21.5% O2 and 78.5% N2. Neatly show your work. Density=PM/RT

32g/mol * 21.5%= 6.88g

28.014g/mol * 78.5%= 21.99g

Mass of air= 6.88g + 21.99g= 28.7099 g Density= PM/RT =(1.01184atm*28.7099g)/(0.08206atm*293.65K) =1.20554 Density=1.2055g/L

Calculation summary: What is the density of air? 1.2055g/L 3) In the following table, copy the result of your Q1 calculation at the bottom of page 2: Volume of flask (L)

0.11225L

Calculate the mass (in grams) of air in the flask. Neatly show your work. Density*V=mass (1.2055g/L*0.11225L)=0.135317g Mass= 0.13532g

Calculation summary: What is the mass of air?

0.13532g

4) In the following table, copy the required value from the data summary at the top of page 2: Mass of flask + cap + air (g) 73.608 Calculate the mass (in grams) of a capped, but completely empty flask (no air or water). Neatly show your work. Mass of flask-mass of air (73.608g)-(0.1352g)=73.473g

Calculation summary: What is the mass of the empty, capped flask? 73.473g 3

NAME

Noah Stegman

Student ID# 2072397

Quiz Section DP

5) In the following table, copy the required values from the data summary at the top of page 2 and the result of your Q4 calculation at the bottom of pg 3: Mass of flask + cap + vapor (g), #1 73.592

Mass of flask + cap (g)

73.473

Mass of flask + cap + vapor (g), #2 73.594 Mass of flask + cap + vapor (g), #3 73.596 Calculate the mass (in grams) of sample (vapor) for Run #1. Neatly show your work for Run #1 and provide your results for all three runs below the box. Mass of flask and cap w/ vapor– mass of flask and cap Run1=(73.592g)-(73.473g)=0.119g Run2=73.594-73.473=0.121g Run3= 73.56-73.473=0.123g

Calculation summary: What is the mass of sample for Run #1?

0.119g

What is the mass of sample for Run #2?

0.121g

What is the mass of sample for Run #3?

0.123g

6) In the following table, copy the required values from the data summary at the top of page 2 and the result of your Q1 calculation at the bottom of page 2 : Barometric Pressure (atm)

1.01184

Volume of the flask (L) 0.11225

Sample Temperature (K) 373.15 Calculate the moles of sample (vapor) in the flask at the time you cap it. Neatly show your work. PV=nRT n=PV/RT n=0.0037092 n=0.00371moles

Calculation summary: How many moles of sample are in the capped flask? 0.00371moles

4

Noah Stegman

NAME

Quiz Section DP

Student ID# 2072397

7) In the following table, copy the results of your Q5 and Q6 calculations on page 4: Mass of sample (g), #1 0.119 Moles of sample (mol) 0.00371 Calculate the molar mass (in g/mol) of your sample (vapor) based on the data for Run #1. Neatly show your work for Run #1 and provide your results for all three runs below the box. Run1 Molar mass= g/mol Molar mass=(0.119g)/(0.00371) Molar mass=32.08216 Molar mass=32.1 g/mol

Run2 Molar mass= (0.121)/0.00371 Molar mass=32.6g/mol

Run3 Molar Mass= (0.123)/(0.00371) Molar mass=33.16 33.2g/mol

Calculation summary: What is the MM based on Run #1?

32.1g/mol

What is the MM based on Run #2?

32.6g/mol

What is the MM based on Run #3?

33.2g/mol

Calculate the average MM of your sample using all three runs. Avg=(M1+M2+M3)/3 =(32.1+32.6+33.2)/3 =32.633333 AvgMM=32.6g/mol

Average MM:

32.6g/mol

8) The possible unknowns are listed below. For each, calculate the molar mass. Name of Compound

Formula of Compound

Molar Mass of Compound

methanol

CH4O

32.04g/mol

acetone

C3H6O

58.08g/mol

ethylacetate

C4H8O2

88.1g/mol

ethanol

C2H6O

46.07g/mol

Based on your comparison of the information in the table above and the average molar mass of the unknown determined from your three trials, what is the identity of your sample? Unknown # from pg 2 data summary: 2

Name of your unknown compound: methanol 5

NAME

Noah Stegman

Quiz Section DP

Student ID# 2072397

9) In the following table, copy the results of your Q7 and Q8 calculations on page 5: Actual average MM of unknown sample:

32.04g/mol

Molar Mass of the 32.6g/mol compound you identified as your unknown: Calculate the % error and comment on the accuracy and precision of your results compared to the molar mass for the compound you identified as your unknown. Identify possible sources of error. %error= (32.6-32.04)/32.04 %error= 1.75% Error could come from not letting the flask dry completely. The methanol could have been contaminated, ethanol is less dense than air, if there is air in the flask, it would increase the molar mass. Another source of error could be not letting the ethanol evaporate completely, or letting too much vapor escape from the flask.

Laboratory Waste Evaluation - Laboratory waste is considered anything generated during an experiment that is disposed of down the sewer drain, thrown in the garbage, collected in a container for disposal by the UW Environmental Health & Safety department, or released into the environment. Based on the written lab procedure and your actions during the lab, list the identity and approximate amount (mass or volume) of waste that you generated while performing this experiment. Kimwipes Paper towels pH strips ~0.25L of Water ~0.4g of Methanol

6...