Why is khp considered monoprotic
Is KHP monoprotic acid?
Potassium hydrogen phthalate also known as KHP is a monoprotic acid.
Does KHP completely dissociate?
KHP dissociates completely in water, giving the potassium cation (K+) and hydrogen phthalate anion (HP− or Hphthalate−). And then as a weak acid hydrogen phthalate reacts reversibly with water to give hydronium (H3O+) and phthalate ions.
What type of standard is KHP?
Potassium Hydrogen Phthalate (KHP) is a classic primary standard substance in that it is readily available in high purity; is relatively inexpensive; is easy to dry; is neither hygroscopic, oxidized by air, nor affected by Carbon Dioxide (thus making it easy to weigh out); does not undergo decomposition during storage; …
What is KHP and why is it used to standardize NaOH?
Solid NaOH is highly hygroscopic (it absorbs water from the air) and thus it cannot be accurately weighed. A KHP sample of known mass (and, therefore, known moles) can be titrated with the NaOH solution to determine very precisely the concentration of the NaOH. This procedure is called standardizing the NaOH solution.
What is KHP used for titration?
A commonly used primary standard for titration with sodium hydroxide solution is the weak acid potassium hydrogen phthalate or KHP (C8H5O4K). In this reaction as well, one mole of KHP completely reacts with one mole of NaOH. The titration of NaOH with KHP involves adding NaOH from the burette to a known volume of KHP.
Is KHP soluble in water?
Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth’s hydrosphere and the fluids of all known living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients.
What makes KHP a better primary standard than 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 is phenolphthalein a useful indicator for titrating KHP with NaOH?
A strong acid- strong base titration is performed using a phenolphthalein indicator. Phenolphtalein is chosen because it changes color in a pH range between 8.3 – 10. It will appear pink in basic solutions and clear in acidic solutions.
How do you standardize a base with KHP?
To Standardize:
Weigh ~0.8 g of dried KHP (MW = 204.23 g/mol) into an Erlenmeyer flask and dissolve in 50-75 mL of distilled water. 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.
Why is KHP the compound of choice for standardizations?
Why is KHP the compound of choice for standardization? It is not hygroscopic, so we can be confident that it will not absorb water meanwhile you weigh it. Why do we use phenolphthalein indicator during the titration? The indicator will let us know when enough NaOH has neutralize the KHP.
Is KHP solution a standard solution?
The concentration of a standard solution is known very precisely. Since KHP is available in very pure form, you can make a standard solution by weighing a precise amount of KHP and dissolving it in water to make a precise volume of solution.
Is KHP chemically stable?
Chemical Stability: Stable under normal temperatures and pressures. Conditions to Avoid: Incompatible materials, dust generation, excess heat. Strong oxidizing agents, nitric acid.
What is the use of phenolphthalein?
Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions. It belongs to the class of dyes known as phthalein dyes.
Why is KHP dried before use?
Why is the KHP stored inside the drying oven? Although potassium hydrogen phthalate is an excellent primary standard for titrations, it is somewhat hygroscopic (absorbs water for the atmosphere). So to obtain an accurate mass of the sample, it is necessary to dry the sample before use.