Molar Volume of Nitrogen Gas

◼ Put on lab coat, and safety goggles

◼ Turn off the mobile phone in lab

◼ Put your school bag in the drawer or cabinet, do not put on aisle

◼ Put pre-lab report on lab bench for TA to check and sign

◼ Hand in “Lab Safety Certification and Identification” with photo, signature,

and contact information on it

Collect:

◼ 2 small test tubes (clean, dry, and cool to r.t.)

◼ Iron stand

◼ 2 extension clamps

◼ 250 mL Erlenmeyer flask

◼ 500 mL Florence flask

◼ Rubber tube with glass tube

* Do not take the extension clamp off the stand on your lab bench1

(2021/03/02 revised)

Objective

Objective:

▪ To determine the molar volume of nitrogen gas at STP

by using chemical reactions and the ideal gas law

Introduction:

▪ Molar volume: the volume of a mole of substance

▪ Standard temperature and pressure (STP): 0oC, 1 atm

▪ Molar volume of an ideal gas is 22.414 L at STP

Techniques:

– Weighing chemicals

– Measuring volume and temperature

– Measuring pressure (By Mercury Barometer)

2

▪ Limiting reagent: sulfamic acid (H2NSO3H, n1 mol)

▪ Excess reagent: sodium nitrite (NaNO2)

▪ Chemical reaction:

NO2− + H2NSO3H → HSO4

− + H2O + N2

n1 n1

▪ Using the number of mole of nitrogen gas (n1), room

temperature (T1), volume (V1) and partial pressure of nitrogen

(PN2), and the ideal gas law to determine the molar volume of

nitrogen gas at STP (VSTP)

Stoichiometry of the Reaction

2 2N atm H OSTP

1 1 1 1

P (V V) (P P ) V1 (atm) V (L)

1 (mol) 273.15 (K) n T n T

+ − = =

Mercury

barometer

Appendix

7

Water collected

in beaker

Limiting reagent Thermometer

3Equations premised on same temperature and pressure before and after the reaction

Apparatus and Setup

4

Lab bench

Fasten by

extension clamp

Florence flask B

Erlenmeyer flask A

Small test tube

Fasten by extension clamp

(Use iron stand on hot plate)

400 mL Beaker D

Step 1:Measuring and Setup

▪ Flask A

Measure 1 g of NaNO2 and

dissolve in 50 mL DI water

▪ Small test tube:

1.0~1.1 g H2NSO3H (limiting

reagent, record accurate

weight by analytical balance)

▪ Fill the rubber tube C with

water and clamp tight

5

Weighing H2NSO3H by Analytical Balance

Put on a beaker

(container)

Close

windshield

& zeroing

(TARE)Display shows 0.0000 g

(Deduction of container’s mass)

Place small

test tube in &

close

windshield

W1: 7.5757 g

(Mass of small test tube)

Use the small end of spatula to put

1 g of H2NSO3H in small test tube

(ca. 5 times)

Place the tube

with chemicals

in and close

windshield

W2: 8.6202 g

(Mass of test tube and H2NSO3H)

Mass of H2NSO3H

W2 - W1 = 1.0445 g

(Five s.f.)

6

Take out

small test tube

Step 2:Check the Water Flow

▪ Fill the Florence flask B and beaker D with water

▪ Setup the equipment as shown

▪ Loosen pinch clamp to check if water can flow freely between

flask B and beaker D; rubber tube C is completely filled with

water, then clamp tight again

▪ Place the test tube into the flask A with the help of tweezers

7

Raise up the beaker

to check the water flow

▪ Check the rubber stoppers is tightly fitted

▪ Loosen pinch clamp, adjust the pressure of the reaction

system to be equal to the atmospheric pressure by adjusting

the water surface of flask B and beaker D to the same level

▪ Tighten pinch clamp on rubber tube C and dispose the water

in beaker; measure the weight of empty beaker

Step 3: Adjust the Pressure

8

Pinch clampPinch clamp

Florence Flask B Beaker D

Adjust Pressure Empty beaker

Adjust the Pressure of System

▪ Check the stoppers

▪ Raise up beaker to

adjust the system

pressure

▪ Tighten pinch

clamp on rubber

tube C

▪ Weigh the empty

beaker9

Check Setup by TA

10Lab bench

* Rotate rubber stopper for 15o to seal up the system

* Check rubber tube is not aged to have cracks

Use a 400-mL

beaker

Water level is at the bottleneck

V ＞250 mL

Place flasks on benchtop and do not let them hang in the air

Fasten flasks by

iron stands and

extension clamps

Step 4: Start the Reaction

11

* Tilt the test tube

* Start reaction

gently

* Loosen pinch

clamp promptly

* Check the water

flow

Collect the

water displaced

until no more

gas evolved

Gas

evolved

Swirl the flask

gently

Reddish-brown NO2(g)

produced by side

Note: Do not twist the rubber tube during the reaction

Note: Volume of water displaced greater than 250 mL 11

▪ Cool the flask A to room

temperature with water bath

▪ Adjust the water levels of

beaker D and flask B to

same level to equilibrium the

system pressure to the

atmospheric pressure

▪ Tighten the pinch clamp

▪ Measure the weight of water

collected in beaker D to

calculate V

▪ Record room temperature

and pressure

Step 5: Adjust to Room Temp. and Atmospheric Pressure

12

1 L beaker V ＞250 mL

Step 6: After Reaction and Post Lab

Measure the wt. of

water and beaker

to calculate V

13

Adjust system temp.

and pressure to room

temp. and

atmospheric pressure

Pour and flush the

waste away quickly

for NO2 may evolved

Notice

▪ Shall you have any questions in operation, feel free to discuss

with TA; do not keep trying and repeat same kind of errors by

yourself

▪ Bring scientific calculators to every experiment

▪ Accomplish calculations and pay attention on the significant

figures and the units used, such as 1.10 g, 359.12 g, and

359.12 mL

▪ Actively offer your questions when hand in lab report to TA

▪ After the lab:

－Clean and return the small test tube

－Clean up the lab bench and hot plate

－Check and replace equipment in the cabinet according to

equipment list

－Tuck in the lab stools underneath the bench 14

Brief report

15

POST-LAB Assignments

◼ When accomplishing the experiment:

1) FIND TA to check your lab record and get signature (Hand

in lab certification and lab report)

2) Find ASSISTANT TA to check your apparatus and clean up,

then get signatures

3) GROUPS ON DUTY shall help TA to recover the lab

environments

▪ Take off lab coat and goggle only when you STEP OUT LAB

▪ Lab report (condensed report):

▪ Subgroup A (person in charge): summit lab report including

prelab report, lab records, and data analysis results

▪ Subgroup B: summit your prelab report

Category Guidelines

I. Prelab

report

1. Indicate the main principles and chemical equations in summary.

2. List the chemicals’ physical, chemical properties, and toxicity.

3. Use the flow chart to explain the procedures concisely.

II. Lab

record

4. Record the data with correct significant figures and units.

5. Record the observations, operation, and reaction condition in

details.

III. Results

&

discussion

6. Process the data correctly, including the equations and calculation.

7. Indicate the final results with correct significant figures and units.

8. Analyze the results and make the appropriate discussion.

9. Plot the results with appropriate XY axis and indicate each curves.

10. Provide the concrete outcome and constructive suggestion.

16

Scoring Rubrics for Lab Report Condensed Report

17

T3 - Mercury Barometer-I

T3 Video on YouTube (Click)

18

T3 - Mercury Barometer-II

⚫ Step 1: Zero adjust

Rotate the Zero Adjusting Knob to adjust the top of the mercury

reservoir just touching the tip of the Zeroing Peg.

⚫ Step 2: Read the height of mercury column by the vernier

➢ Adjust the height of the Movable Scale so that the bottom of the

slide piece is just even with the top of the meniscus.

➢ Read the main scale on the right of vernier. As in Fig. T3-1, the

bottom of slide piece indicates the height of mercury is between

76.1 cm and 76.2 cm.

➢ Read the movable scale on the left of vernier where the lines

match up with the main scale, i.e. 6 (the percentile of

measurement). Therefore, the atmospheric pressure reads 76.16

cm-Hg.

⚫ For more precisely measurement, one should refer to manual of

barometer to make correction of temperature.

19

◼ To maintain calibration, never move the

balance.

◼ Do not overload the balance. Maximum load of

an electronic balance in lab is usually 610 g.

◼ Check to see that the balance is level and

clean before use.

◼ Warm up the balance for 30 min before use.

T9 - Electronic Balance

◼ Put weighed object in the center of weighing pan. Read digital readout for mass.

◼ Use folded weighing paper, beaker or bottle as container while weighing. Do not

put chemicals on the pan directly.

◼ Always allow an object that has been heated to return to room temperature

before weighing it.

◼ Keep the balance and its case scrupulously clean. The balance area has a soft

brush for this purpose.

◼ Do not invert balance upside down to avoid damage to the parts inside.

◼ Analytical balance is an instrument with high precision with maximum load of

210 g. Close its windshields while zeroing and weighing.

Analytical Balance

(±0.0001 g)

T9 Video on YouTube (Click)

Electronic Balance

(±0.01 g)

T10 Video on YouTube (Click)

20

T10 - Weighing Chemicals

◼ Read the label on bottle of the chemicals carefully to avoid taking the wrong one.

◼ Use folded weighing paper, beaker, or weighing bottle to hold solid chemicals.

◼ Use a clean and dry spatula to take solid chemical.

◼ Use a clean and rinsed dropper to take liquid chemicals.

◼ Keep the electronic balance clean and control the amount of chemicals taking to

avoid excess weighing, dripping, and scattering around.

◼ Unless specifically directed to the contrary, never return any excess reagent to

the original bottle to avoid contamination. Put it in specified waste can.

◼ Keep well closed after taking chemicals.

◼ Keep the reagent shelf and the laboratory balance clean and neat at all times.

Clean up any spillages immediately.

21

T11 - Graduated Cylinder

▪ Use a dropper to add the liquid to the calibration line, or to draw out excess

fluid.

▪ Slowly incline the cylinder to provide a steady stream of liquid from the spout

to transfer the liquid to another container. Be careful not to splash.

▪ Continue inclining the cylinder until it is vertical and hold for about several

seconds.

▪ Touch the drop at the tip of the spout to the wall of the receiving container.

▪ Wash and brush the graduated cylinder after use.

T11 Video on YouTube (Click)

▪ Clean the graduated cylinder and rinse twice with small

amount of the liquid to be taken.

▪ Carefully place the liquid to be measured into the

graduated cylinder with a steady stream against a wall

near the calibration line, being careful not to splash.

▪ When the level is just below the calibration line, stop

for a few minutes to let the liquid drain from the walls of

the container.