Tell me how to conduct a titration with these solutions please (1 Viewer)

[2006hsc]

im not good with titrations...
can you tell me the procedure of titrating with these solutions anyone?

common solution of HCl of known concentration
unknown solution
phenolphthalein solution indicator


can sum1 tell me what goes in what?
eg. HCl goes into burette while 3 drops of the indicator goes with the unknown in the conical flask......right?

 

[theworldisround]

First step in exams, write the equation HCL + NaOH --> NaCl + H2O
(we are assuming HCL of UNKNOWN CONCENTRATION is reacting with the NaOH of CONCENTRATION 0.1M in this reaction)

Pipette 25 mL of HCL into the conical flask
Add 50mL of NaOH to the burette.

REMEMBER: rinse all equipment with the solution that would go into it. ie. rinse burette with NaOH, and pipette with HCL. Rinse the conical flask with distilled water ONLY.

Add 3 drops of phenophthalein to the HCL in the conical flask.
Add the NaOH from the burette into the conical flask, until the colour of the solution in the flask turns from colourless to pink.
Record how much NaOH was used from reading the burette. This is known as the titre value.
Repeat the experiment at least three times to ensure reliability.

Calculations:
Assuming your results for the NaOH are 24mL, 27mL, and 28mL respectively.

We discard first result as it is clearly an outlier, hence the average titre is 27.5mL.

From the equation, we observe that one mole of HCL reacts with one mole of NaOH.

No. of moles of NaOH = concentration times volume
= 0.1 times 0.0275 <-- notice it is converted to litres
= 0.00275 moles

Therefore no. of moles of HCL also = 0.00275 moles

Therefore concentration of HCL = moles divide by volume
= 0.00275 divide by 0.025 <--volume in conical
= 0.11 M