General Chemistry Lab - Lab 2: Analytical Chemistry PDF

# General Chemistry Lab - Lab 2: Analytical Chemistry ## Asst. Lect. Arwa Fadil ## Analytical Chemistry ### Classification of Analysis: * **Qualitative Analysis:** Determination of chemical identity of the species in the sample. * **Quantitative Analysis:** Determination of the amount of specie...

# General Chemistry Lab - Lab 2: Analytical Chemistry ## Asst. Lect. Arwa Fadil ## Analytical Chemistry ### Classification of Analysis: * **Qualitative Analysis:** Determination of chemical identity of the species in the sample. * **Quantitative Analysis:** Determination of the amount of species or analytes, in numerical terms. In order to perform quantitative analysis, complete qualitative analysis is needed. ### Classification of Quantitative Method of Analysis: * **Volumetric Method:** Volume is measured or used to determine amount of sample via concentration. * **Gravimetric Method:** Mass is measured. * **Instrumental Method:** Uses an instrumental technique to assay the amount of sample, such as visible spectrophotometer based upon light absorption. ### Classification of Qualitative Method of Analysis: * Qualitiative research epistemologies which are non-oriented proof. * Qualitative research strategies are to interpret and reveal concepts and meanings rather than generalizing accidental relationships. * Qualitative research techniques can't fall into numbers. ## Quantitative Analysis ### Definitions and Terms: * **Standard solution:** A reagent of exactly known composition used in a titration. * **Primary standard:** A highly purified chemical compound. * **Standardization:** A process whereby the concentration of a standard solution is determined by titrating with a primary standard solution. ### Requirements of a primary standard: 1. Highest purity. 2. Stable and not attacked by atmosphere. 3. Not hygroscopic. 4. Available and not expensive. 5. High equivalent to minimize weighing errors. ### Concentration Units: * **Normality:** The number of equivalent weights contained in one liter of solution. $Normality = \frac{wt/equivalent weights}{volume of solution(L)}$ * **An equivalent weight of an acid:** $\frac{gram molecular weight} {no. of (H)atoms that can be replaced}$ * **An equivalent weight of a base:** $\frac{gram molecular weight} {no. of (OH)groups that can be replaced}$ * **Molarity:** The number of gram molecular weights or the number of moles of solute in one liter of solution. $Molarity = \frac{moles of solute} {volume of solution(L)}$ $Moles of solute = \frac{weights} {gram molecular weight}$ * **Formality:** The number of gram formula weights per liter of solution. * **To calculate the Normality of concentrated acid:** $Normality = \frac { m.wt \times % \times sp.g}{1000}$ * **To prepare an acid from concentrated acid:** $N_1V_1 = N_2V_2$ ## Experiment (1): Preparation of Standard Solution from a Solid ### Introduction The solution must be prepared in such a way that it's concentration is known to a high degree of precision for many experiments. The purpose of this lab is to give you practice at the techniques involved in the preparation of such a solution. ### Purpose To prepare 100 ml of 0.1 mol/L Sodium chloride solution. ### Experiment Materials * Balance * Sodium chloride * Distilled water * 100 ml volumetric flask * Funnel * Spatula * 150 ml beaker * Dropper * Wash bottle ### Procedure: 1. Calculation the mass of solute required. 2. Place a clean dry 150 ml beaker on the balance and tare the balance. 3. Add solute to the beaker until the required mass is shown on the scale. 4. Add about 75 ml of distilled water to the beaker. Stir to dissolve the solid. Use the funnel to transfer the solution into a clean volumetric flask. Be sure to rinse the rod and beaker into the flask. 5. Add distilled water until the water is approximately 1 cm below the etched mark on the neck of the volumetric flask. 6. Carefully add distilled water until the bottom of the meniscus is on the mark (use dropper). 7. Place the stopper on the volumetric flask and mix the solution thoroughly by inverting and shaking the flask. *Don't add water to a level above the line on the neck of the flask.* ### Analysis * Calculate the concentration of your solution. * Why was it necessary to invert the volumetric flask? * Why should the final solution be left stopper? * If we filled the flask to above the line how would this have changed the concentration of the solution? The document includes a diagram depicting the steps for preparing the solution, but this was unable to be replicated with markdown formatting.