Chem011-labrep2.docx

CM011L: CHEMISTRY FOR ENGINEERS (LABORATORY) 1ST Quarter SY 2018-2019

Experiment No.2 Volatile Liquid Glennmar P. Otilla CM011L-B16

Department of Chemical, Biological, and Materials Engineering and Sciences Mapua University ABSTRACT They are many ways to calculate the molar mass of a certain substance or mixture but for this given experiment the researchers use the ideal gas law formula to get the molar mass of a volatile liquid, in which it follows the formula of PV=nRT, P is pressure, V is volume, n is the number of moles, R is a constant and T is temperature. To determine the molar mass first we need to prepare the setup of the experiment first, the researchers need to prepare the beaker , Erlenmeyer flask , Bunsen burner and etc. for them to properly observe the needed data for the experiment , carefully follow the procedure to avoid miscalculations and error along the way, when the setup is done observe thoroughly especially when the water inside the beaker is boiling for this is the most crucial part of observation , the researchers need to see the evaporation of gas inside the flask to know where to stop or to keep going, in this part also the researchers need to know the temperature and the volume of the water inside the beaker, the researchers found out that the molar mass of the volatile liquid is 56.36 g/mol in which the experiment is successful for the researchers has succeeded to get the molar mass of the volatile liquid , the researchers recommend to study in advance before conducting this experiment. Keywords: volatile liquid, molar mass, gas law, moles , temperature INTRODUCTION One of the properties that helps in identifying a

aqueous substance which is volatile, while in gaseous

substance is its molar mass. In a case of a volatile

form we can measure the volume, pressure and

liquid, a common method to calculate its molar mass is

temperature of the said substance. The researchers

by using the formula of the ideal gas law, PV=nRT. It

also used the ideal gas law to calculate the moles of the

can be easily converted into gas for it is made from an

substance, After determining the number of moles the

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CM011L: CHEMISTRY FOR ENGINEERS (LABORATORY) 1ST Quarter SY 2018-2019

researchers can use the ideal gas law to calculate the

Iron stand

1

molar mass of the volatile liquid.

Graduated cylinder (50mL)

1

According to Jean Baptiste Dumas, a French chemist, in his analytical procedure, the liquid is vaporized into a fixed-volume vessel at a measured temperature and barometric pressure, believe that the number of moles of a substance is the number of atoms inside the element . this study only limits itself from the unknown

Erlenmeyer flask with foil and 1 rubber (125mL) Thermometer

1

Barometer

1

Beaker (600mL)

1

Gas pump

1

substance inside the flask, any substance that the

The researchers first measured the weight of the

researchers wish to determine aside from the said

Erlenmeyer flask with a foil cover on its top and a rubber

substance that is given to them , will not be covered by

placed around it which it weighs eighty five point fifty

this study.

seven grams (85.57)g. then the researchers poured

The null hypothesis of this study is that it will be impossible to calculate the molar mass of the volatile liquid.

300Ml tap water to the 600mL beaker , the boiling chips are included inside the beaker and the 300 ml water . the next step is to prepare the iron stand, iron clamp and the Bunsen burner in which the beaker is put on top of it in order for it to be boiled . the Erlenmeyer flask with

MATERIALS AND METHODS

foil and rubber band that is containing our Isopropyl The researchers used the following materials and

alcohol is put inside the beaker slightly below the water

apparatuses in performing th experiment

level . this is where the real experiment will begin. After

Table 1: Materials and equipment used in the experiment Materials/ Equipment

the preparation , open the Bunsen burner then bring to boil the water inside the beaker, after 5 minutes of the first boil measure its temperature using the

Quantity/ Measurement

Tap water

300mL

Boiling chips

3

Isopropyl alcohol

5mL

Bunsen burner

1

Iron clamp

1

Experiment 02│ Group No. 5│ Date of Experiment 03-10-19

thermometer then after that turn off the Bunsen burner then let it cool down for 3 minutes then measure again the mass of the Erlenmeyer flask (do it with the foil and rubber still with the flask , measure it without the rubber ,then lastly measure it without the foil and the rubber), also check its volume by using the 50mL graduated cylinder , continuously pour down everydrop of excess

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CM011L: CHEMISTRY FOR ENGINEERS (LABORATORY) 1ST Quarter SY 2018-2019

water inside the beaker to the graduated cylinder to know the volume of the 125mL flask

Figure 3: boiling stage Figure 1: pouring of unknown liquid TOPIC QUESTIONS 1. Part A.1. The mass of the flask (before the sample into the flask) is measured when the outside of the flask is wet. However, in Part B.3, the outside of the flask is dried before its mass is measured. A.

Will the mass of vapor in the flask be

reported as too high or too low, or will it be unaffected? Explain. Figure 2 : final setup (before bringing to boil )

-The water outside the flask will be added to its mass of the vapor, therefore mass of the vapor would be possibly be too high.

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CM011L: CHEMISTRY FOR ENGINEERS (LABORATORY) 1ST Quarter SY 2018-2019

B. Will the molar mass of vapor in the flask be

A.

How will this oversight in the procedure

reported as too high or too low, or will it be

affect the mass of vapor measured in Part B.3,

unaffected? Explain.

too low, too high, or unaffected? Explain.

-As the mass increases, the molar mass will be also

-Piercing aluminum foil with large pencil-size

increased. Since the flask is not dried after

holes will cause a large amount of vapor to escape.

vaporizing the liquid, the mass will increase, and

This leads the mass of vapor to decrease, hence it

the molar mass will be too high.

will be reported as too low.

2.

Part A.1. From the time the mass of the

B.Will the reported molar mass of the liquid be

flask is first measured in Part A.1 until the time

reported too low, too high, or unaffected?

it is finally measure in Part B.3, it is handled a

Explain.

number of times with oily fingers. Does the lack

-As the mass of vapor decreases, the molar mass

of proper technique result in the molar mass of

of the liquid will decrease also. For that reason, the

the vapor in the flask being reported as too high

molar mass of the liquid will be measured as too

or too low or as unaffected? Explain.

low.

-The molar mass increases thus the mass of foil,

4.

rubber band, and vapor increase. Having the lack

with vapor only when it is removed from the

of proper technique will recorded the molar mass

hot water bath in Part B.3. However, when the

of the vapor in the flask as too high.

flask cools, some of the vapor condenses in the

3.

Part A.2. The aluminum foil is pierced

flask. As a result of this observation, will the

several times with large pencil-size holes

reported molar mass of the liquid be too high,

instead of pin-size.

too low, or unaffected? Explain.

Part B.2. The flask is completely filled

-Some of the vapor condenses in the flask when it cools, wherein it is a part of an experiment to be

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observe. The vapor only changes to a liquid, which

-In the formula of PV=nRT, moles and volume are

does not really affect the mass of the liquid. As a

directly proportional. When the volume increases,

result, the molar mass of the liquid will be

molar mass will also increase. Considering the

unaffected since nothing is being added or

volume of vapor in the actual experiment is 158

removed.

mL, which is higher than 125 mL in the given

5.

Part B.2. Suppose the thermometer is

question. Therefore if the flask is been assumed to

miscalibrated to read 0.3 ℃ higher than actual.

be 125 mL, the molar mass of the unknown liquid

Does this error in calibration result in the

will be recorded as too low than the actual result.

molar mass of the vapor in the flask being

7.

reported as too high, too low, or as unaffected?

barometer is recorded higher than it actually

Explain.

is. How does this affect the reported molar

-The error in calibration will measure the molar

mass of the liquid: too high, too low, or

mass of the vapor as too low, since it has been

unaffected? Explain.

miscalibrated 0.3℃ higher than actual result. With

-Pressure and moles are directly proportional.

the actual result, it must be recorded the molar

When the recorded barometer is higher than its

mass of vapor as too high.

actual, the molar mass of the liquid will be

6.

reported as too high. Since the pressure increases,

Part C.1. If the volume of the flask is

assumed to be 125 mL instead of the measured

Part C.2. The pressure reading from the

the molar mass will increases also.

volume, would the calculated molar mass of the unknown liquid be too high, too low, or unaffected

by

this

experimental

Explain.

error?

RESULTS AND DISCUSSION the researchers only conducted 1 trial , using all the data and observe traits before , during and after the experiment is concluded. The researchers started to

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compute the molar mass of the volatile liquid by using

https://mapua.blackboard.com/bbcswebdav/pid-

the ideal gas formula PV=nRT.

540851-dt-content-rid11306429_1/courses/CM011L_A9_1Q1819/CM011%

The researcher started to convert first to know the

20Laboratory%20Manual.pdf

needed data in accuracy the researchers started by converting the millimeter of mercury (mmHg) to the

https://prezi.com/k1zbpyrazfld/molar-mass-of-a-

atmosphere (atm). Then, converted the value of the

volatile-liquid/

calculated volume of the flask from mL to L. Lastly, they converted the calculated temperature in degree Celsius to Kelvin. In which, R is the universal constant, P is the atmosphere calculated by the researchers, V is the volume of the flask in liters and T is the temperature converted to Kelvin of the vapor. The researchers only gathered 0.0055 mol of vapour (n) and a mass of 0.31g ( mass of vapour) and a molar mass of 56.36g/mol. Resulting for a successful experiment CONCLUSIONS AND RECOMMENDATIONS In conclusion, reject the null hypothesis for the researchers computed the molar mass of the compound which is (56.36g/mol) The researchers recommend to know the background of the experiment by studying the basic formulas, gas laws, and proper computing of molar mass, volume and temperature to avoid miscalculations and disparities as you go along the experiment. REFERENCES

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