Primary standard potassium hydrogen phthalate

For this experiment you will need a minimum of 3 to 4 g of primary standard potassium hydrogen phthalate (KHP) for three titrations. Place at least 6 g of it in a weighing bottle and dry in a drying oven for 2 h. Your instructor may choose to dispense this to you. 

B. A solution of NaOH was standardized by titration of a known quantity of the primary standard, potassium hydrogen phthalate ... 

Consider the example shown in Figure 1.1 for the quantitation of a maleic acid solution, containing a known concentration of the primary standard potassium hydrogen phthalate (KHP). A primary analytical standard is a material of very high purity for which the mass of the compound can be used directly in the calculation of solution concentration.The area of the KHP peak is divided by 4.0, the number of protons that contribute to the KHP aromatic resonances, so that its normalized area is 1773.1. Similarly the maleic acid peak area is normalized by dividing by 2.0 to give a normalized area of 1278.3. A simple proportion can then be established to solve for the concentration of maleic acid ... 

Acids and bases in Table 10-3 can be purchased in forms pure enough to be primary standards. NaOH and KOH are not primary standards because the reagent-grade materials contain carbonate (from reaction with atmospheric CO2) and adsorbed water. Solutions of NaOH and KOH must be standardized against a primary standard. Potassium hydrogen phthalate is convenient for this purpose. Solutions of NaOH for titrations are prepared by diluting a stock solution of 50 wt% aqueous NaOH. Sodium carbonate is relatively insoluble in this stock solution and settles to the bottom. 

Bromocresol green indicator Dissolve 100 mg in 14.3 mL of 0.01 M NaOH and dilute to 250 mL with distilled water. Concentrated (37 wt%) HCl 10 mL/student Primary standards Potassium hydrogen phthalate ( 2.5 g/student) and sodium carbonate ( --l.O g/student) 0.05 M NaCl 50 mL/student... 

Step 2 Weigh out an appropriate amount of an acidic material, suitable for use as a primary standard, such as potassium hydrogen phthalate (KHP). 

For standardizing a base solution, primary standard grade potassium biphthalate is a popular choice. Also called potassium hydrogen phthalate, potassium acid phthalate, or simply KHP, it is the salt representing partially neutralized phthalic acid and is a monoprotic weak acid. The true formula is KHC8H404. Figure 5.8 shows the chemical structure of phthalic acid and KHP. The reaction with a base is as follows ... 

The P in KHP refers to phthalate. The phthalate ion is a benzene ring with two carboxyl groups on adjacent carbons. See Figure 5.8. Potassium hydrogen phthalate (KHP) is useful as a primary standard because it possesses all the qualities sought in a primary standard. See Section 4.5.2. 

Note A good number of Standard Samples, including primary standards, such as arsenic trioxide, benzoic acid, potassium hydrogen phthalate, sodium oxalate, are available as ... 

Potassium hydrogen phthalate has many uses in analytical chemistry. It is a primary standard for standardization of bases in aqueous solutions. Its equivalent weight is 204.2. It also is a primary standard for acids in anhydrous acetic acid. Other applications are as a buffer in pH determinations and as a reference standard for chemical oxygen demand (COD). The theoretical COD of a Img/L potassium hydrogen phthalate is 1.176mg O2. 

Potassium hydrogen phthalate is a primary standard used to measure the concentration of NaOH solutions. Find the true mass of potassium hydrogen phthalate (density = 1.636 g/mL) if the... 

Dry primary-standard-grade potassium hydrogen phthalate for 1 h at 110°C and store it in a desiccator. 

Standardization of a sodium hydroxide solution using potassium hydrogen phthalate as a primary standard (p. 143)... 

From the viewpoint of primary standards for ordinary analysis, acceptable purity depends on the substance. Many contain at least 99.9-1-% of the major component, for example, potassium hydrogen phthalate, potassium chloride, or calcium carbonate but cholesterol of high purity is 99.4%, and bilirubin 99%. 

Potassium hydrogen phthalate as a primary standard for bases Potassium hydrogen phthalate, C6H4COOKCOOH, is used almost exclusively as the primary... 

When a solution of standard base is used only for titration of strong acids, a small amount of carbonate is not a serious source of error provided the end point is taken with an indicator that changes color at a pH of about 4 or 5. For standardizing such carbonate-containing solutions, potassium hydrogen phthalate is an unsuitable primary standard. An alternative is pure potassium chloride, which is passed through a cation-exchange column, converted to hydrochloric acid, and titrated with the sodium hydroxide. 

Figure 1.1. 600 MHz NMR spectrum of potassium hydrogen phthalate (KHP) and maleic acid dissolved in D2O. The KHP is a primary standard by which the maleic acid concentration can be quantitated. The data represents 8 FTDs coadded into 28,800 points (zero-filled to 32K points) across a spectral width of 7200.1Hz. An exponential multiplier equivalent to 0.5Hz...

It is highly desirable to establish a set of pH buffer solutions which can be used at temperatures above 100 °C. Thus far, little has been done to develop the necessary sets of the high-temperature buffer systems as primary standards. Only a 0.05 mol-kg potassium hydrogen phthalate solution has been adopted by lUPAC as an appropriate primary buffer system to be used at temperatures up to about 225 °C. However, the acid dissociation constants of many organic and inorganic buffers have been measured with the hydrogen-electrode concentration cell (see discussion below) and these results are currently available for developing the secondary pH standards to 250 °C. 

Potassium hydrogen phthalate is a solid, monoprotic acid frequently used in the laboratory as a primary standard. It has the unwieldy formula of KHCgH404. This is often written in shorthand notation as KHP. K 25.0 mL of a potassium hydroxide solution are needed to neutralize 2.26 grams of KHP, what is the molarity of the potassium hydroxide solution ... 

Several operational standard buffers have been defined and their pH values assigned by the use of cells without liquid junctions according to Covington et al. and Kristensen et al. [9, 10]. The primary standard, 0.05m aqueous potassium hydrogen phthalate (KHPh) was established. One implementation of the cell nsed for assignment of the reference standard pH is ... 

Dissolve 10.21 g of analytical reagent quality (primary buffer-standard specification) potassium hydrogen phthalate, KHCgH404, in distilled water and make the volume to 1000 ml in a measuring flask. Store in a glass bottle. The solution is stable almost indefinitely in the absence of evaporation. The formation of a slight turbidity introduces no error. 

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