Sodium hydroxide
Phenolphthalein
White tile measuring cylinder hydrochloric acid
Conical flask
Method
- First I have to collect the equipment, Funnel, hydrochloric acid, sodium hydroxide, bosshead / clamp, stand, conical flask, burette, white tile, goggles, measuring cylinder and Phenolphthalein.
- I put the burette on the bosshead. On top I put the funnel so can put in the hydrochloric acid. Under the burette I put the white tile and the conical flask.
- I measure 10 cm3 of sodium hydroxide using the measuring cylinder. Then I pour it into the conical flask. I put five drops of phenolphthalein in the sodium hydroxide.
- I put the burette to a sensible height to put in the hydrochloric acid. I pour 50cm3 in the burette.
- I put the burette into a drop into the sodium hydroxide as I stir it. The colour of the sodium hydroxide is pink and the experiment is complete when it’s clear.
- After 10cm3 of hydrochloric acid the solution should go clear if I done it right. I will repeat this five more time.
Risk assessment
The chemicals I used in this experiment are hydrochloric acid, Sodium hydroxide and Phenolphthalein as the indicator. The chemicals can be very dangerous if it is at a high concentration.
Sodium hydroxide:
It is a very harmful corrosive; it can cause burns as well as permanent damage to eye if contact with it. The E.U classification for sodium hydroxide is corrosive. To prevent potential risk I am going to wear goggles in this experiment.
Hydrochloric acid:
Hydrochloric acid is very corrosive and can damage eyes if it comes into contact. It’s also lethal to fish from 25 mg/l up also toxic for aquatic organisms due to pH shift.
To prevent potential risk I am going to wear goggles in this experiment.
Phenolphthalein:
Phenolphthalein is safe to use and it doesn’t appear to have any safety risks.
Result table
Number of times the Cm3 of hydrochloric
Experiment was repeated acid needed
1 10
2 9.7
3 10.2
4 9.8
5 10.4
Average 10.02
Calculations
Hcl = hydrochloric acid
Naoh = sodium hydroxide
Mr – NaoH Na + O + H 40g
Mr – Hcl cl + H 36.5g
No. of moles of Naoh
Volume x molarity
0.02L x 0.5M = 0.01 moles
(20ml)
Analysis
To neutralise 10cm3 of sodium hydroxide I theoretically need 10cm3 of hydrochloric acid. My results show I came up with 10.2cm3 of hydrochloric acid which I feel human error effected my results.
Conclusion / Evaluation
My aim is: to find the volume of hydrochloric acid needed to neutralise sodium hydroxide. I found how much hydrochloric acid was needed to neutralise sodium hydroxide.
According to my results 10.2 cm3 of hydrochloric acid is needed to neutralise 10cm3 of sodium hydroxide. As I stated I theoretically need 10cm3 of which means I made errors. Human error was the main cause of my results since I could have measured wrong,
My task is to determine the concentration of limewater solution. Here is the information I've been given:
- you are provided with 250 cm*3 limewater which has been made so that it contains approx. 1g dm*-3 of calcium hydroxide
- also available is hydrochloric acid which has a concentration of exactly 2.00 mol dm*-3(the acid is too concentrated to be used so must be diluted)
My main question is how should i dilute this HCl and to what concentration to use in the titration. I'm also confused on what it means when the limewater contains 1g dm-3 of calcium hydroxide. What would i do to the limewater in the experiment.
This is only the planning part of the coursework so i only need to show my method, apparatus, safety precautions etc.
you dilute the acid.. any low concentration will do.. i would go for 0.1M/0.25M... better not have it tooo concentrated for safety reasons. fill the burette with the Acid and using a pippete, put 25cm3 of the limewater into a conical flask with a few drops of indicator (phenophthalin(howeva u spell it)) and titrate till eqivalence point (till the drop that turns the solution pink permanently)
read the volume of acid used from the burette. the concentration of acid is known so find the number of moles
now using write out the equation and use stochiometry to find mumber of moles of Ca(OH)2 present.
your volume was 25cm3 (with the pippete) so calculate concentration by c=n/v
yea basically its the same thing coz the number of moles of acid needed will never change... so if its more concentrated, less acid will be needed, but n=CV .... you will always get the same number of moles in the end, no matter what concentration you use.. but dont have it too concentrated or else youll have a highly exothermic vigourous reaction... keep away from that!
