How do you calculate the molarity of NaOH from a titration with KHP?
The number of moles of NaOH is found by multiplying the moles of KHP by the mole ratio of NaOH to KHP given by the above, balanced chemical reaction. 3. The molarity of the NaOH solution is found by dividing the moles of NaOH by the liters of NaOH solution required to reach the endpoint of the titration.
What does KHP and NaOH make?
The reaction between an acid and base produces a salt and water, something that you may have heard before. In the reaction that you will be investigating, the acid is potassium hydrogen phthalate (KHP), and the base sodium hydroxide (NaOH)….Stoichiometry and Solutions.
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Why is phenolphthalein a good indicator for titration KHP with NaOH?
Phenolphthalein is colorless in acidic solution, but turns red in basic solution. When one drop more NaOH is added than is required to react with the KHP in a sample, the sample becomes basic and the indicator changes color.
How will you know when to stop titration the KHP solution with the NaOH solution in the Buret?
Keep the mass of KHP used as constant as possible. Calculate the concentration of your NaOH solution and the average deviation (as in lab 1). If the average deviation is less than 0.0002 M, you can stop.
How do you standardize NaOH with KHP calculations?
To Standardize: Record the amount of KHP and water used. Add 4 drops of indicator into the flask and titrate to the first permanent appearance of pink. Near the endpoint, add the NaOH dropwise to determine the total volume most accurately.
How do you find the concentration of NaOH in a titration?
Step 1: Calculate the amount of sodium hydroxide in moles
- Amount of solute in mol = concentration in mol/dm 3 × volume in dm 3
- Amount of sodium hydroxide = 0.100 × 0.0250.
- = 0.00250 mol.
- The balanced equation is: NaOH(aq) + HCl(aq) → NaCl(aq) + H 2O(l)
- So the mole ratio NaOH:HCl is 1:1.
Why is KHP used in titrations?
KHP is slightly acidic, and it is often used as a primary standard for acid–base titrations because it is solid and air-stable, making it easy to weigh accurately. It is not hygroscopic.
Why do we use KHP to standardize NaOH?
Potassium hydrogen phthalate makes for a good primary standard because it is stable, high in purity, non-hydroscopic, highly soluble, non-toxic, high in molecular weight, cheap, and available.
Why phenolphthalein gives colour at end point?
Furthermore, it turns pink when it comes in contact with a substance of a pH of 8.2 and becomes purple at an even higher pH. Moreover, this change in colour is a result of ionization; that alter the charge and shape of Phenolphthalein molecule.
What is the purpose of titrating the pure KHP with the NaOH solution in Part A?
In the first standardization the molarity of a sodium hydroxide solution (NaOH) will be determined by titrating a sample of potassium acid phthalate (KHP; HKC8H4O4) with the NaOH. In the second procedure the standardized NaOH will be used to determine the molarity of a hydrochloric solution (HCl).
Why do we standardize NaOH with KHP?
Since NaOH solutions cannot be prepared by mass to be an exact concentration (solid NaOH is too reactive), you then standardize your NaOH solution by titrating weighed samples of a primary standard acidic substance, potassium hydrogen phthalate (KHC8H4O4, “KHP”, molar mass 204.2 g).
Why did we have to standardize the NaOH solution with KHP?
The base is very hygroscopic, water absorbing. Additionally, the resulting solution tends to absorb carbon dioxide from the air, which neutralizes some of the base. Hence, we first standardize the base against an appropriate primary standard.
What is the best method for determining the concentration of NaOH solution?
One method for concentration determination of sodium hydroxide solutions is titration, where correct and precise results are neither trivial nor quick. Besides, the operator is exposed to the caustic sample. Another method is the determination of the solution’s density, and, derived therefrom, its concentration.
What is the role of KHP in titration?
KHP is slightly acidic, and it is often used as a primary standard for acid–base titrations because it is solid and air-stable, making it easy to weigh accurately.
Why is standardization necessary in titration?
The so-called titer determination or standardization of a volumetric solution used for titration is one of the most important preconditions for reliable and transparent titration results. Accurate and reliable titration results are only achievable when we work with the exact concentration of the volumetric solution.
What color will the solution of potassium phthalate and phenolphthalein appear?
The resultant Acidic solution was transparent, with a small amount of undissolved granules of KHP. As the transparent NaOH solution came into contact with transparent phenolphthalein in the KHP solution, it turned pink which on shaking became transparent.
What does the faint pink color indicates in titration?
In the titration of acetic acid with aqueous NaOH, phenolphthalein is used as the indicator. Phenolphthalein is nearly colorless in acidic solution, but turns pink at a pH of about 8. This indicates that the base has neutralized all the acid.
Why do we see pink in titration?
Titration results in pink colour, due to the addition of an acid-base indicator Phenolphthalein. Phenolphthalein turns colourless to brilliant pink as the solution turns from acidic to basic.
Why is KHP used to standardize NaOH?
% Uncertainty of KHP Mass = (0.01/m KHP) x 100
Why do we use NaOH in titration?
Why do we use NaOH in titration? It is a strong alkaline reagent and produces a sharp change in pH which makes titration easier to do. Is NaOH an acid or base? NaOH is a base because when dissolved in water it dissociates into Na+ and OH- ions. It is the OH- (hydroxyl ion) which makes NaOH a base.
How much of NaOH were used in the titration?
Precisely weigh out approximately 1.000 g potassium acid phthalate (KHP). About 10 mL of NaOH should be used in the titrations. The NaOH solution’s concentration is about 0.5 M. The molar mass of KHP is 204.23 g/mol, and it has one acidic hydrogen per molecule.
What is standardization of NaOH and why is it important?
Normality = Number of gram equivalents ×[volume of solution in litres]-1