Titration potassium hydrogen phthalate

In this experiment the overall variance for the analysis of potassium hydrogen phthalate (KHP) in a mixture of KHP and sucrose is partitioned into that due to sampling and that due to the analytical method (an acid-base titration). By having individuals analyze samples with different % w/w KHP, the relationship between sampling error and concentration of analyte can be explored. 

A titration requires a solution whose concentration is known. In Example the NaOH solution used as the titrant was known to be 0.1250 M. A titrant of known concentration is known as a standard solution, and the concentration of such a solution is determined by a standardization titration. In a standardization titration, the solution being titrated contains a known amount of acid or base. An excellent acid for standardization is potassium hydrogen phthalate, KHCg H4 O4. This substance, a carboxylic acid that contains one weakly acidic hydrogen atom per molecule, is easily obtained as a highly pure solid. A known number of moles can be weighed on an... 

A biochemist needed to standardize a solution of KOH. A sample of potassium hydrogen phthalate weighing 0.6745 g was dissolved in 100.0 mL of water and a drop of indicator was added. The solution was then titrated with the KOH solution. The titration required 41.75 mL of base to reach the stoichiometric point. Find the molarity of the KOH solution. 

C04-0031. To check the results of the first standardization, the biochemist repeated the titration. This time, a mass of 0.7015 g of potassium hydrogen phthalate dissolved in 135 mL of water required 43.36 mL of the base. Find the molarity and decide if the two results are consistent. 

C04-0141. A student prepared 1.00 L of a solution of NaOH for use in titrations. The solution was standardized by titrating a sample of potassium hydrogen phthalate whose mass was 0.7996 g. Before titration, the buret reading was 0.15 mL. When the indicator changed color, the buret reading was 43.75 mL. Calculate the molarity of the NaOH solution. 

C04-0157. As a final examination in the general chemistry laboratory, a student was asked to determine the mass of Ca (0H)2 that dissolves in 1.000 L water. Using a published procedure, the student did the following (1) About 1.5 mL of concentrated HCl (12 M) was added to 750 mL of distilled water. (2) A solution of KOH was prepared by adding approximately 1.37 g KOH to 1.0 L distilled water. (3) A sample of potassium hydrogen phthalate (185.9 mg) was dissolved in 100 mL of distilled water. Titration with the KOH solution required 25.67 mL to reach the stoichiometric point. (4) A 50.00-mL sample of the HCl solution prepared in step 1 was titrated with the KOH solution. The titration required 34.02 mL of titrant to reach the stoichiometric point. (5) The student was given a 25.00-mL sample of a saturated solution of Ca (0H)2 for analysis. Titration with the HCl solution required 29.28 mL to reach the stoichiometric point. How many grams of calcium hydroxide dissolve in 1.00 L of water ... 

It takes 47.03mL of a base to titrate 2.000g of potassium hydrogen phthalate (KHC H404). What is the normality of the base ... 

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. 

Elemental composition K 30.51%, C18.75%, H 0.79% O 49.95%. An aqueous solution of potassium hydrogen phthalate may be measured by titration against a standard solution of potassium hydroxide. 

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

How many grams of potassium hydrogen phthalate should be weighed into a flask to standardize 0.05 M NaOH if you wish to use 30 mL of base for the titration ... 

Derive the following equation analogous to those in Table 11 -6 for the titration of potassium hydrogen phthalate (KJHP-) with NaOH ... 

Weigh out four —0.51 -g portions of potassium hydrogen phthalate and dissolve each in —25 mL of distilled water in a 125-mL flask. Each sample should require —25 mL of 0.1 M NaOH. Add 3 drops of phenolphthalein indicator (Table 11-4) to each, and titrate one of them rapidly to find the approximate end point. The buret should have a loosely fitted cap to minimize entry of C02. 

Titration of a 0.7865 g sample of pure potassium hydrogen phthalate requires 35.73 ml of a NaOH solution. Calculate the molarity of the NaOH solution. This acid-base reaction is... 

NaOH in 1 L water. Standardize as follows accurately weigh to the nearest 0.001 g approximately 1 g potassium hydrogen phthlate, KC8H504, MW = 204.3 g/mole, and dissolve it in 20 mL water. Add a few drops of phenolphthalein and titrate the potassium hydrogen phthalate with the prepared NaOH solution. The normality (N) of the NaOH solution is calculated as follows ... 

When 2.818 g of potassium hydrogen phthalate (symbolized here as KHPh molar mass = 204.2 g/mol) is titrated with KOH solution, it takes 31.74 mL of the base to achieve the end point. Calculate the concentration of the KOH solution. 

Sodium hydroxide solution is usually standardized by titrating a pure sample of potassium hydrogen phthalate (KHP), an acid with one acidic hydrogen and a molar mass of 204.22 g. It takes 34.67 mL of a sodium hydroxide solution to titrate a 0.1082-g sample of KHP. What is the molarity of the sodium hydroxide ... 

A student titrates an unknown amount of potassium hydrogen phthalate (KHQH4O4, often abbreviated KHP) with 20.46 mL of a 0.1000 M NaOH solution. KHP (molar mass = 204.22 g/mol) has one acidic hydrogen. How many grams of KHP were titrated (reacted completely) by the sodium hydroxide solution ... 

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. 

Sodium hydroxide is one of the bases conunonly used in the laboratory. However, it is difficult to obtain solid sodium hydroxide in a pure form because it has a tendency to absorb water from air, and its solution reacts with carbon dioxide. For these reasons, a solution of sodium hydroxide must be standardized before it can be used in accurate analytical work. We can standardize the sodium hydroxide solution by titrating it against an acid solution of accurately known concentration. The acid often chosen for this task is a monoprotic acid called potassium hydrogen phthalate (KHP), for which the molecular formula is KHC8H4O4. KHP is a white, soluble solid that is commercially available in highly pnre form. The reaction between KHP and sodium hydroxide is... 

The pH titration curves for the determination of the equilibrium constants in HjO were recorded with a Metrohm E536 potentiograph connected to a Metro-hm E665 dosimat and a Metrohm 6.0222.100 combined macro glass electrode. The pH calibration of the instrument was done with the mentioned buffer solutions at pH 4.00, 7.00 and 9.00. The titer of the NaOH used was determined with potassium hydrogen phthalate. 

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. 

Potassium hydrogen phthalate, KHCgH O, is a solid acidic substance that reacts in a 1 1 mole ratio with bases that have one hydroxide ion. Suppose that 0.7025 g of potassium hydrogen phthalate is titrated to the equivalence point by 20.18 mL of a KOH solution. What is the molarity of the KOH solution ... 

---