Lab #5 Partly Scanned for Q and A PDF

# Procedure ## General Instructions - Use small quantities of solids as indicated. - Estimate the amounts instead of weighing them. Your teacher will display sample quantities as a basis for comparison. - Use your graduated cylinder to measure out the first few volumes of liquids so that you can g...

# Procedure ## General Instructions - Use small quantities of solids as indicated. - Estimate the amounts instead of weighing them. Your teacher will display sample quantities as a basis for comparison. - Use your graduated cylinder to measure out the first few volumes of liquids so that you can get a feel for the depth of liquid in a test tube corresponding to a given volume. - Estimate the volumes of liquids once you have practiced. - Rinse out your graduated cylinder thoroughly with tap water followed by a final rinse with distilled water. - Clean test tubes with detergent and a test-tube brush if necessary. - Rinse test tubes with distilled water. Turn them upside down in your rack to drain until ready for them. - Dry test tubes by holding them with a test-tube holder and gently heating them in a burner flame. Never dry a graduated cylinder by heating it in a flame. Use a clean towel if necessary. - Use test tubes to hold reaction mixtures. Do not perform reactions in a graduated cylinder. - Heat produced in reactions may crack the cylinder, and precipitates that may form are often not easily removed. - Dispense reagents by using the dropper or spatula supplied with each bottle. - Do not use your own dropper or share droppers among reagent bottles. - Never return excess reagents (solid or liquid) to the stock bottle. - Discard excess reagents in the waste container(s). - Discard liquids in the sink only if specifically instructed to do so. Even some water-soluble liquids should be discarded in a designated container. - Mix reagents by stirring them with a glass stirring rod unless indicated otherwise. Rinse off the rod after each use. ## Specific Instructions - Observe and record the color and properties of the reactants, what happens when they are mixed or heated, and the color and properties of the products when any reaction has ceased. - Note odors by following the procedure outlined in Lab 1. Never place the open end of a test tube directly under your nose. ## Part I: Heating sugar and salt water **A.** Place enough table sugar (sucrose; $C_{12}H_{22}O_{11}$) into a dry test tube to cover the bottom of it. Use an old or chipped test tube if possible since cleaning is difficult. 1. Heat the sugar for 1-2 minutes using a burner flame. 2. Record your observations. **B.** Pour enough $NaCl$ into a dry 50 mL beaker to cover the bottom of it. 1. Add about 6 mL of water to the beaker. Stir the solution until the salt is dissolved. 2. Using a support stand setup, heat the salt water until the water has nearly evaporated. **Caution:** Do not allow the water to boil away. Heating a beaker to dryness may cause it to break. 3. Record your observations. ## Part II: Heating magnesium and zinc **A.** Obtain a 1 cm piece of magnesium (Mg). 1. Using a pair of tongs, heat the metal in a burner flame. **Caution:** As you put the magnesium into the flame, keep your eyes averted. Do not look directly at the magnesium while it burns. 2. Record your observations of the metal before and after heating. **B.** Obtain a 1 cm piece of zinc (Zn). 1. Using tongs, heat the metal in a burner flame for 1 minute or until you notice a change. 2. Record your observations of the metal before and after heating. ## Part III: Observing physical/chemical changes **A.** Fill a test tube half full of water. Drop 2-3 pieces of calcium into the test tube. Record observations and conclusions. **B.** Obtain 5 mL each of 1.2 M KI solution and 0.60 M Pb(NO3)2 solution in separate test tubes. Pour the KI solution into the Pb(NO3)2 solution. Record observations and conclusions. **C.** Add 1 mL of 6 M NH3 solution to a test tube containing 3 mL of 1 M CuSO4 solution. Seal the tube with a stopper; mix; and observe. Record observations and conclusions. **D.** Add 5 drops of sodium sulfate solution to a test tube containing 3 mL of CuSO4 solution; seal with a stopper and mix. Record observations and conclusions. ## Part IV: Performing additional suggestions (optional) **A.** Heat a small amount of steel wool as in Part II. Record observations and conclusions. **B.** Investigate other combinations as in Part III. ## Caution: Do not allow HCl or NaOH to come into contact with your skin. If either chemical does, flush the area with large amounts of water for at least five minutes. Do not rub. 1. Combine a copper metal strip with 5 mL of dilute (6 M) hydrochloric acid. Record observations and conclusions. 2. Combine 0.2 g sodium bicarbonate (NaHCO3) with a few drops of 6 M HCl. Record observations and conclusions. 3. Combine 3 mL dilute hydrochloric acid with 3 mL of 6 M sodium hydroxide (NaOH) solution. Record observations and conclusions.