Determination of the Concentration of Hydrochloric Acid

 January 16, 2020

Purpose

        The purpose of this lab is to find out the unknown concentration of the given HCl solution. Therefore, this will be tested by titrating the given HCl solution with the standardized NaOH solution.

Materials

-        1 volumetric flask

-        1 electronic balance

-        sodium hydroxide

-        1 scoopula

-        distilled water

-        1 pipette and bulb

-        10 mL graduated cylinder

-        1 burette clamp

-        a piece of white paper

-        labels

-        1 retort stand

-        1 burette and burette tip

-        125 mL Erlenmeyer flask

-        150 mL beaker

-        30 mL of 0.15 mol/L HCl solution

-        1 wash bottle

-        1 funnel

-        phenolphthalein indicator pipette

Procedure

Part A

1.         Rinse equipment with distilled water

2.         Calculate the mass range with a range of 0.07 mol/L – 0.1 mol/L NaOH solution

3.         Use a scoopula to measure a range of 1.4 g to 2.0 g of NaOH with an electronic balance

4.         Record the mass of the NaOH and mix the NaOH with distilled water to make 500 mL of NaOH solution

5.         Transfer the solution into the provided bottle which is clean

6.         Label the bottle with group members’ names

 

Part B

1.         Rinse the burette first with distilled water, then rinse it with NaOH solution. 

2.         Repeat above step three times

3.         Collect 30 mL HCl in a flask

4.         Label all of the equipment

5.         Fill NaOH solutions in the burette with a funnel below the marking of 0 mL

6.         Record the initial volume on the burette

7.         Measure 10 mL of HCl with a graduated cylinder

8.         Transfer 10 mL of HCl into the Erlenmeyer flask

9.         Add a few drops of the indicator into the Erlenmeyer flask of 10 mL HCl 

10.     Place the flask beneath the burette tip and place the white paper underneath the flask

11.     Titrate NaOH into the Erlenmeyer flask of while swirling it gently

12.     When the faintly pink colour appears, close the stopcock and record the final volume

13.     Calculate the difference between the initial volume and the final volume

14.     Repeat step 6 to step 13 three times

15.     Pour the faintly pink colour solution in the Erlenmeyer flask into the sink

16.     Rinse all the equipment with distilled water

17.     Return all the equipment

 

Part C

1.         Rinse the burette first with distilled water, then rinse it with NaOH solution. 

2.         Repeat above step three times

3.         Collect 30 mL unknown concentration of HCl in a flask

4.         Label all of the equipment

5.         Record the unknown sample number

6.         Fill NaOH solutions in the burette with a funnel below the marking of 0 mL

7.         Record the initial volume on the burette

8.         Measure 10 mL of HCl with a graduated cylinder

9.         Transfer 10 mL of HCl into the Erlenmeyer flask

10.     Add a few drops of phenolphthalein into the Erlenmeyer flask of 10 mL HCl 

11.     Titrate NaOH into the Erlenmeyer flask while swirling it gently

12.     When the faintly pink colour appears, close the stopcock and record the final volume

13.     Calculate the difference between the initial volume and the final volume

14.     Repeat step 7 to step 13 three times

15.     Pour the solution in the Erlenmeyer flask into the sink

16.     Rinse all the equipment with distilled water

17.     Return all the equipment

 

Data and Results

 

Table 1 Data obtained from the measurement and calculation

	Concentration of the NaOH solution	Mass of the NaOH
Range	0.07 mol/L to 0.1 mol/L	1.4 g to 2.0 g
Actually used	0.081 mol/L	1.61 g

 

Table 2 Data for the titration of 0.15 mol/L HCl with the unknown concentration of NaOH solution

Reading (mL)	Trial 1	Trial 2	Trial 3
Final reading	23.0	42.6	39.6
Initial reading	2.5	23.0	19.7
Volume added (final - initial)	20.5	19.6	20.0

 

Table 3 Data for the titration of unknown concentration HCl with standardized NaOH solution

 (unknown sample number: __________)

Reading (mL)	Trial 1	Trial 2	Trial 3
Final reading
Initial reading
Volume added (final - initial)

Analysis

Part A

The concentration of NaOH solution between the given range 0.07 mol/L to 0.1 mol/L

→ The mass range of NaOH

500 mL = 0.500 L

C = n / V, n = m / M

The mass range of NaOH: 1.4 g to 2 g

Actually used 1.61 g of NaOH

→The concentration of NaOH 

=1.61 g of NaOH/(22.99+16.00+1.01)g/mol /0.500L

= 0.0805 M 

→ 0.0805 M of NaOH

Part B

Balanced chemical equations: NaOH_(aq)+ HCl_(aq)→ NaCl_(aq)+ H₂O_(l)

Each Trial 10 mL of 0.15 mol/L HCl

10 mL = 0.010 L

C = n / V

The mole of HCl = 0.010 L×0.15 mol/L = 0.0015 mol

The coefficient ratio of NaOH : HCl = the mole ratio of NaOH = 1:1

The mole of HCl = the mole of NaOH = 0.0015 mol

Trial 1:

The volume added: 23.0 mL - 2.5 mL = 20.5 mL = 0.0205 L

The concentration of NaOH = 0.0015 mol / 0.0205 L = 0.073170731 M → 0.073 M

Trial 2:

The volume added: 42.6 mL - 23.0 mL = 19.6 mL = 0.0196 L

The concentration of NaOH = 0.0015 mol / 0.0196 L = 0.076530612 M → 0.077 M

Trial 3:

The volume added: 39.7 mL - 19.7 mL = 20.0 mL = 0.0200 L

The concentration of NaOH = 0.0015 mol / 0.0200L = 0.075 M

The average concentration of NaOH in three trial = (0.073M + 0.077M + 0.075M)/3 = 0.075M

Part C

Balanced chemical equations: NaOH_(aq)+ HCl_(aq)→ NaCl_(aq)+ H₂O_(l)

Each Trial 10 mL of unknown concentration HCl

10 mL = 0.010 L

The average concentration of NaOH = 0.075M

The coefficient ratio of NaOH : HCl = the mole ratio of NaOH = 1:1

C = n / V

Trial 1:

The volume added: ____mL - ____mL = ______mL = ______ L

The mole of NaOH = 0.075 mol/L × _____ L = _______ mol = the mole of HCl

The concentration of HCl = _____ mol / 0.010 L = _____ mol/L

Trial 2:

The volume added: ____mL - ____mL = ______mL = ______ L

The mole of NaOH = 0.075 mol/L × _____ L = _______ mol = the mole of HCl

The concentration of HCl = _____ mol / 0.010 L = _____ mol/L

Trial 3:

The volume added: ____mL - ____mL = ______mL = ______ L

The mole of NaOH = 0.075 mol/L × _____ L = _______ mol = the mole of HCl

The concentration of HCl = _____ mol / 0.010 L = _____ mol/L

The average concentration of HCl = (____ mol/L + ____ mol/L + ____ mol/L)/3 = ____ mol/L

The unknown concentration of HCl: ______ mol/L

 

Conclusion

This lab aims at determining the concentration of the given HCl solution. After preparing and standardizing the NaOH solution, the main procedure of titrating the given HCl solution with the standardized NaOH solution was carried in the lab to obtain the data. Based on the results of calculating the mass and concentration (HCl and NaOH), the unknown concentration of the given HCl solution was          mol/L.