POST LAB 3 CHM3120C

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University of South Florida *

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3120C

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Chemistry

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Dec 6, 2023

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Perla Bathani CHM3120C Post lab 3 Mahmoud mohammed Lab 3. Practice Titration, Potassium Hydrogen Phthalate (KHP) Part 1: Preparation of 0.1 M carbonate-free NaOH solution, and drying KHP. Part 2: Titration (Standardization of NaOH solution) Trial 1 Trial 2 Trial 3 Mass of a weighing paper (or dish) 0.4140g 0.4132g 0.4125g Mass of a weighing paper (or dish) and dried KHP 1.1210g 1.1143g 1.1860g Mass of dried KHP 0.7070g 0.7021g 0.7061g # of moles, KHP 0.0035 mol 0.0035 mol 0.0036 mol Volume of NaOH (Initial buret reading) 0 ml 0 ml 0 ml Volume of NaOH (Final buret reading) 34.80 ml 34.90 ml 34.92 ml Volume of NaOH used 34.80 ml 34.90 ml 34.92 ml Molarity of the NaOH solution 0.10057 0.10029 0.10023 % Error NA NA NA Average Molarity of the NaOH solution and STD:_0.10036 ± __0.00018___________ Calculations: Average= 0.10057+0.10029+0.10023 = 0.10036 mol 3 Standard deviation= √ ( 0.10057 − 0.10036 ) 2 + ( 0.10029 − 0.0036 ) 2 + ( 0.10023 − 0.10036 ) 2 ÷ √ 3 − 1 =0.00018 ml Post lab questions: 1- What is the correct way to handle a burette and an Erlenmeyer flask during a titration? For accurate and secure titration procedures, it's essential to handle a burette and an Erlenmeyer flask properly. Before filling the burette, first rinse it with the titrant solution

to remove any air bubbles. Take careful note of the beginning volume. To ensure thorough mixing, hold the burette vertically with one hand on the stopcock and the other hand swirling the flask. Slow down the titrant flow as you get closer to the desired endpoint, then add it dropwise while whirling till the endpoint is reached. Take close note of the ultimate volume. The Erlenmeyer flask should be placed on a stable surface, any necessary reactants added, and placed beneath the burette. If you overshoot the endpoint, keep the flask steady, stir gently to combine, and refrain from refilling the contents. Clean the flask for future use and properly dispose of waste solutions after the titration is finished. Always follow the precise procedure instructions and use the proper safety equipment when handling chemicals. These methods are necessary for obtaining accurate and secure titration results. 2-Provide at least 2 different examples of desiccant material and at least 2 different styles of desiccator and explain how they function differently. Desiccant materials: 1- Silica gel is a type of desiccant that is frequently used. It is made up of tiny, porous silica beads with a strong attraction to water molecules. By trapping water vapor inside of its porous structure, silica gel absorbs moisture and effectively lowers the humidity in the desiccator. 2-An additional desiccant substance is calcium chloride. It is a salt that rapidly absorbs moisture from the air because it is very hygroscopic. When calcium chloride is exposed to the air inside a desiccator, it dissolves in the water vapor that is taken in and creates a concentrated brine solution that settles to the bottom of the desiccator. Styles of Desiccators:

1- Vacuum desiccator: Made to create a low-pressure or vacuum atmosphere inside the desiccator. It often features a vacuum valve and thick walls that are airtight. When a vacuum pump is connected and turned on, air from the desiccator is evacuated, reducing pressure. As a result, the boiling point of water is lowered, which causes stored moisture to evaporatively dry up inside-placed materials more quickly. 2- Gas pure desiccator: It employs a steady stream of dry, inert gas to push moist air out of the desiccator rather than producing a vacuum. Through an entrance and outlet, the gas flow is controlled. The desiccator maintains a low-humidity environment by removing moisture-laden air when the dry gas passes past it. Applications where maintaining an inert environment is crucial are suited for gas purge desiccators. 3- Why is water boiled prior to the preparation of NaOH standard solution? Explain briefly. There are two crucial reasons to boil water before creating a sodium hydroxide standard solution. First, it assists in purifying the solution by removing dissolved gases and contaminants from the water. Second, boiling water raises its temperature, which also raises NaOH's solubility in the liquid. Hot water makes it simpler to dissolve more sodium hydroxide in the solution, producing a more concentrated standard solution. Sodium hydroxide is more soluble in hot water than in cold water. This is crucial when precise measurements are necessary for experiments or analytical applications that call for concentration precision. The NaOH standard solution can be prepared with the necessary concentration and purity thanks to boiling water. 4- What is standardization in acid-base chemistry? What constitutes a standard in analytical chemistry? Give types and examples .

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By titrating a solution against a previously established standard solution of a different substance, standardization in acid-base chemistry refers to the process of exactly determining the concentration of a solution, frequently an acid or a base. This standard solution, which is often a main standard with known purity, serves as a guide for determining the correlation between the volume of the standard solution needed to neutralize the analyte and its concentration. Standards are essential in analytical chemistry because they serve as benchmarks for calibrating equipment and confirming measurement accuracy. These standards can come in a variety of shapes, each fulfilling a particular function in laboratory analysis and quality control, including primary standards, secondary standards, certified reference materials, working standards, and internal standards. Standardization is a cornerstone of analytical chemistry in a variety of businesses because it ensures the dependability and accuracy of analytical measurements. 5- In the following graph depicting a titration curve for weak acid vs strong base (titrant), explain the chemistry occurring (in regard to chemicals and their states, equilibria) at four points a, b, c, and d indicated. At point a: Initial Solution You begin with the weak acid CH3COOH. Most of its molecules are CH3COOH. Some CH3COOH molecules have changed into H+ ions and CH3COO- ions, while the majority are still CH3COOH molecules. At point b: Near the Equivalence Point You get closer to the equivalence point as you keep adding the strong base (NaOH). More CH3COO- ions and water (H2O) have been produced as a result of some CH3COOH molecules reacting with NaOH. However, not all CH3COOH has yet responded.

At point c: Point of Equivalence You've now added enough NaOH to completely react with all the CH3COOH. All the CH3COOH has been converted to CH3COO- ions, and the water-based solution is sodium acetate, a salt. At point d: After the Equivalence Point As you keep adding NaOH, the solution becomes more fundamental. The solution still contains extra OH- ions from the NaOH. As you add more NaOH, the solution becomes more basic.