Question

Microscale techniques: In today's experiment we will be using very small amounts of chemical reactants. This method is generally less expensive and more environmentally-friendly than traditional "test tube" chemistry. Some of the waste products produced in today's experiment, particularly those containing lead and barium, are harmful to the environment. By using such small amounts of chemical reactants we generate far less waste than by using larger scale methods. Procedure 1. Put on your safety goggles. Be sure to wear them for the duration of the experiment| 2. Obtain a chemical reaction grid from the chemical cart. Most of your chemical reactions will be carried out on this plastic sheet. Make sure the grid is clean and dry. Also, clear away any clutter in your work area. 3. Obtain a dropper bottle which contains one of the ten reagents we will be using in today's experiment. These chemicals include HCl, Na2CO, Pb(NO3)2, FeCl, KNO, KI, H2SO, AgNOs, BaCl2, and NaOH. It does not matter which chemical reagent you begin with, so long as you keep track of which ones you still need to use. Be sure to thoroughly read and understand the following directions before you proceed. 4. Place one drop of your chemical reagent in each box underneath the formula of the chemical you have obtained. You will also do this to the left of the formula of this chemical. For example, for HCl you would place one drop in each box on the first row. For Na2CO3, you would place one drop in the box in the upper left-hand corner, and then one drop in each box on the second row. 5. Obtain another dropper bottle containing one of the other reagents. Add a drop of this solution to the appropriate boxes on the grid, just like you did in the previous step. Do not touch the tip of the bottles to the surface of the plastic grid or directly on to one of the other drops. This may contaminate the solution and give other students misleading results! The tip of the bottle should be held about half a centimeter above the grid when each drop is applied. If you make a mistake, such as placing a drop in an incorrect box, you should remove the liquid by using the dropper in your lab drawer to suck up any drops. Then, gently dab the area clean with a small piece of paper towel. 6. Repeat step 5 for every reagent until you have used each of them. At this point, each box in the grid should contain a mixture of exactly two solutions. Some of the solutions have reacted with each other while others have not. Special instructions for acid-base reactions: It may not be evident that a reaction occurs between hydrochloric acid and sodium hydroxide or between sulfuric acid and sodium hydroxide. A reaction does occur in each case, although there will be no visual evidence of this since the main product is water. You should carry out these two reactions in a test tube. For each reaction, add three drops of each reactant to the test tube, then look at the glass above the surface of the mixed solutions. Steam should condense in the tube. Reactions between acids and bases generally produce heat, and this steam is evidence of this fact. You should also notice that the test tube has become warm to the touch. The products of these two reactions (and only these reactions) may be poured down the drain.