This study is about how to standardise a Sodium Hydroxide ( NaOH ) solution by titrating it with pure sample of Potassium acid Phthalate ( KHC8H4O4 ) . This experiment has two subdivisions. The first subdivision is to standardise the Sodium Hydroxide by titration. Three sample of 0. 7 – 0. 9 g of solid KHP are topographic point into each of the three numbered Erlenmeyer flasks. 50 milliliter of distilled H2O are added to each three of it from graduated cylinder and invariably agitate it until the KHP solution are wholly dissolve.
2 beads of phenolphthalein are add to each flask. Titrate each of the three flasks at the same time with NaOH solution to the terminal point with the first visual aspect of a swoon visible radiation pink that persist for 15 seconds. The coloring material will melt as CO2 from the air are dissolve in the solution. The 2nd subdivision is about standardisation of diluted Sodium Hydroxide ( NaOH ). These subdivisions are rather similar to subdivision 1 but this method is titrating utilizing a diluted Sodium Hydroxide which is diluted for 5 times.
Aim:
- To standardise the Na hydroxide solution with K H phthalate by utilizing titration technique.
- To cipher the concentration of the standard solution after titration is complete.
Materials:100 milliliters Erlenmeyer Potassium Hydrogen Phthalate. KHP50 milliliter Graduated cylinderDistilled WaterTitration Set Up SpatulaBurette Top lading balance ± 0. 01g50 % w/w NaOH
Procedure:
- Standardization of Na hydrated oxide ( NaOH ).I. Three samples of solid KHP were weighed accurately of approximately 0. 7 g to 0. 9 g into each of the three clean. numbered Erlenmeyer flasks. two. Each flasks were added 50 milliliter of distilled H2O from a graduated cylinder and the flask were shaken gently until the KHP is dissolved. Then 2 beads of phenolphthalein were added into each of the flask. three. Each of them were titrated with the NaOH solution to the terminal point with the first visual aspect of a swoon ( light ) pink colour that persists for 15 2nd. The colour faded as CO2 from the air dissolved in the solution. four. The mean molar concentration. the standard divergence and comparative criterion divergence ( S/X ) was calculated.
- Standardization of Diluted NaOHI. A diluted standardisation NaOH were prepared in a 250 milliliter volumetric flask. two. Three samples of solid KHP were weighed accurately of approximately 0. 7 g to 0. 9 g into each of the three clean. numbered Erlenmeyer flasks. three. Each flasks were added 50 milliliter of distilled H2O from a graduated cylinder and the flask were shaken gently until the KHP is dissolved. Then 2 beads of phenolphthalein were added into each of the flask. four. Each of them were titrated with the NaOH solution to the terminal point with the first visual aspect of a swoon ( light ) pink colour that persists for 15 2nd. The colour faded as CO2 from the air dissolved in the solution. v. The mean molar concentration. the standard divergence and comparative criterion divergence ( S/X ) was calculated.
DiscussionIn order to find the concentration of a solution. there must be something to compare it against ( benchmark ). This benchmark is referred to as a criterion. Sodium hydrated oxide (a base) is typically used as a criterion to find the concentration of acids. When an acid and base react. they form salt and H2O. acid + base > salt + H2OIn a titration the volume of a solution added to a reaction is measured utilizing a buret. A buret is a long tubing with a valve ( turncock ) at one terminal at one terminal that can be used to command the flow. Burettes are typically calibrated in millilitres.
The acid and base are reacted together until one of the two is wholly reacted. That point is called the end point that is impersonal. If any extra acid or base is added. the solution will so go acidic or basic depending on which was added in surplus. To visually find the end point. an index is added to the reaction. An index is a chemical that changes colourss at a peculiar pH. When merely a bantam surplus of the acid or base is added beyond the completion of the reaction. the index alterations colour. The sum added from the buret at this point is called the end point.
In order to utilize a standardised solution. the solution must be prepared. After readying of the criterion. the exact concentration of the standard solution must be determined. In this experiment. a Na hydrated oxide solution ( NaOH ) will be prepared. In order to standardise the Na hydroxide solution. there must be a substance used to standardise against. This substance will be potassium H phthalate ( KHP ). KHP is an organic acid that is solid and therefore. easy weighed.
Using basic stoichiometry. the moles of NaOH in the solution can be determined from the moles of KHP added to the reaction.
Note the grinder relationship. For every one mole of KHP. it would take one mole of NaOH to respond it wholly.Since we weigh out a peculiar mass of KHP. We can easy cipher the moles of KHP we will utilize as the criterion. The molecular mass of KHP is 204. 2 amu.
Since for every one mole of KHP used it takes one mole of NaOH to respond with it. if the moles of
KHP is known. the moles of NaOH is known.
moles of KHP = moles of NaOHIn the titration. the NaOH is added bead by bead utilizing the buret. The buret indicates how much NaOH is being added to the KHP. At the point where all the KHP has been reacted ( end point ) any extra NaOH will turn thesolution BASIC. The index. phenolphthalein. turns the solution from clear to tap in a basic solution. This is called the end point.
The volume of NaOH added to the KHP is read off the buret in millilitres ( end point ) and converted to litres ( litres = milliliter / 1000 ).
The concentration ( molar concentration ) of the Na hydroxide solution can now be determined.
This standardised NaOH solution can now be used as a criterion for the finding of acerb concentrations.
Examples
0. 8 gms of KHP is titrated with 40 milliliter of the unknown NaOH solution. What is the molar concentration of the NaOH solution?
Solution
At the terminal of this experiment. pupil found that a diluted Na hydrated oxide takes more clip to standardise when titrating the solution ( in nowadays of light pale pink ) comparison to pure sample of Na hydroxide solution. At the beginning of the experiment. pupils have theoretically predicted that diluted Na hydrated oxide will take much longer clip to standardise comparison to pure Na hydrated oxide.
So the theory is acceptable. Student besides learns how to decently standardise the Na hydrated oxide whether it is pure sample or diluted solution and accomplish the intent of this experiment to standardise with K H phthalate by titration technique and to cipher the concentration of the standard solution after titration is complete. Following clip to better the information and the consequences of this experiment. pupil should carefully weigh the Potassium acid phthalate to the accurate measuring and patiently titrate the solution non to o.d. .
Appendix
- Titration can be defined as a process in which one solution is added to another solution until the chemical reaction between two solutes is complete. The concentration of one solution is known and that of the other solution is unknown.
- Titrant can be defined as a solution of known concentration which is added ( titrate ) to another solution to find the concentration of a 2nd chemical species.2 ) 25. 00 mL x 4. 50 mol H2SO41000 milliliter soln x 2 mol NaOH1 mol H2SO4 ten 1000 milliliter soln1. 420 mol NaOH x 158 milliliter of 1. 420M NaOH.
