ACID-BASE LAB NOTEBOOK

Transcription

1 N I C O L E T A Y L O R May 5th, May 7th, 2012 ACID-BASE LAB NOTEBOOK PROJECT: WHO YOU GONNA CALL? Dexter-Pinckney Road, Pinckney, MI telephone: 734/272/8293 taynic13@newtech.pinckneyschools.org

2 Abstract The purpose of this report is to summarize the Acid-Base laboratory experiment. The data we were first presented was background information about strong acids, ph, salts, and neutralization. All strong acids are composed of a group one metal and a hydroxide. A list of strong acids may include, HCl, HBr, HI, HNO3, H2SO4 and HClO4. ph we learned in the last lab is used to describe the acidic or basic nature of a solution. Salts are compounds of a metal and a non-mental element. Finally neutralization is a reaction in which equal amounts of acid and base react with each other. Introduction In this lab we are going to experiment with ph values. Svante Arrhenius was the first to create a theoretical model for acids and bases in Prior to this chemically opposite substances were described in properties such as taste. In this lab we will test Arrhenius s theory that pure water dissociates to some extent to produce hydrogen ions, H+ and hydroxide ions, OH-. There are six objectives for this experiment. First: Perform a neutralization reaction. Second: Perform reactions of acids and bases on various materials. Third test various solutions with acid-base indicators. Fourth: Measure the ph of various common materials. Fifth: Perform dissociation reactions of salts and test the solution s ph. Finally the sixth objective is to prepare buffer solutions and measure their buffer capacities. Test Tube Glass Stir Rod Litmus Paper Plastic Dropper EvaporationDish Materials and Methods Test Tube - This thin glass tube, closed at one end is used in this experiment to hold several different solutions. Solutions such as NaOH, HCI, and NaC2H3O2. Reactions also take place within these tubes. Glass Stir Rod - This pole is used to stir solutions and transfer small amounts of solutions. In our experiment it is used a couple times. First to stir the NaOH and then to touch the solution to litmus paper. Litmus Paper - Litmus paper is a strip of paper stained with litmus. Litmus is an indicator and it is used to indicate the acidity of a substance. In our lab litmus paper is first used to test the acidity of NaOH and HCI. Plastic Droppers - Droppers are usually used to transfer small amounts of a liquid from one container to another. In this experiment a dropper is used to blow air bubbles through a test tube. Evaporating Dish - A small ceramic dish in which liquids are heated over a flame so that they evaporate, leaving a solid residue. In this lab the dish is used to evaporate the combined solution of NaOH and HCI. 1

3 Bunsen Burner ph Paper Litmus Paper Bunsen Burner - The bunsen burner is used to heat things. In this lab the evaporation dish is heated as well as a glass rod to confirm the presence of sodium ions. ph Paper - ph paper is used to indicate the ph of a substance. In this lab ph paper is used in Part B to test the ph of five different substances. Glass Plates - These are used to hold drops of indicators and different solutions in order to find the ph range of each solution. Data Tables Part A SOLUTION RED PAPER BLUE PAPER Hydroxide Solution (NaOH) Stayed Red Turned Red/pink Hydrochloric Acid Solution (HCI) Turned Blue/purple Stayed Blue SOLUTION CHLORINE IONS SODIUM IONS Dissolved Sample Blue/white clouding - yes Yellow flame -yes Part B SUBSTANCES PH VALUE Borax Soap-Household Ammonia Vinegar Baking Soda Tums ph 10 - Base ph 2 - Acid ph 9 - Base 2

4 Unknown SUBSTANCES PH VALUE Part C INDICATORS SODIUM HYDROXIDE HYDROCHLORIC ACID Phenolphthalein Separates and turns orange Turns White Methyl Orange Nothing Turns Pink Methyl Red Turns Brown Turns Red Methyl Blue Turns Purple Turned Dark Blue Universal Indicator Turns Dark blue/purple Turns Red Part D SOLUTIONS INITIAL PH VALUE ADDED HYDRO- CHLORIC (HCI) PH VALUE ADDED SODIUM HYDROXIDE (Na OH) PH VALUE Solution A ph 5 ph 1 ph 14 Solution B ph 9 ph 1 ph 12 Solution C ph 6 ph 1 ph 13 Solution D ph 7 ph 1 ph 12 Deionized Water ph 7 ph 1 ph 13 Concluding Questions 1. We were left with table salt, NaCl. We know this because when we tested for chorine and sodium both came out positive. 2. To clean up hard-water deposits containing calcium carbonate we would use vinegar. Calcium carbonate acts like a base and to clean up a base you need to neutralize it by using an acid. Vinegar is more acidic than household ammonia so that s why we chose vinegar. 3. Most of the cleaning agents were classified as a base. Some did come out neutral but that could be due to to much water in the solution. 3

5 4. c. CA + H2O --> COH + A- + H+ because it is the only reaction that shows an H+. H+ is used for acids and to lower ph you have to make it more acidic. Pre-Lab Questions 1. Acid: a chemical substance that neutralizes alkalis, dissolves some metals, and turns litmus red, corrosive or sour tasting. Base: A substance capable of reacting with an acid to form a salt and water, or of accepting or neutralizing hydrogen ions. Salt: Any chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or other cation. Buffer: A solution that resists changes in ph when acid or alkali is added to it. Typically involve a weak acid or alkali together with one of its salts. 2. ph tells you the acidity or basic of a solution. This is based on a scale of one to fourteen, with one to six being acidic, eight to fourteen being basic, and seven being neutral. 3. The formula for ph is -log [H+]. 4. The strength of an acid depends on how it separates into ions in the water. In a strong acid, most of the molecules break up into solutions. In a weak acid, fewer molecules break up into ions. A strong acid produces a high concentration of hydrogen ions. 5. I predict that a solution with a higher ph than the paper can test would cause the paper to change to the color of the highest ph available. In this case I think the solution with a ph of 8 would turn the paper to show 2.5, the highest ph available. 4