If the glassware is not clean, partially fill with a few milliliters of soap solution, and rotate the buret/pipet so that all surfaces come in contact with the soap.Rinse with tap water, followed by several portions of distilled water. If the burets are still not clean, they should be scrubbed with a buret. If the pipet cannot be cleaned, it should be exchanged.In the subsequent procedure, it is important that water from rinsing a pipet/buret does not contaminate the solutions to be used in the glassware. This rinse water would change the concentration of the glassware’s contents. Before using a pipet/buret in the following procedures,rinse the pipet/buret with several small portions of the solution that is to be used in the pipet/buret. Discard the risings.Acid Base Titration
B. Preparation of the Sodium Hydroxide SolutionClean and rinse the 1-L bottle and stopper. Label the bottle “Approx. 0.1M NaOH.” Put about 500ml of distilled water into the bottle.Weigh out approximately 4 g (0.1 mol) of sodium hydroxide pellets (caution!) and transfer to the 1-L bottle using a powder (wide-stem) funnel. Stopper and shake the bottle to dissolve the sodium hydroxide. When the sodium hydroxide pellets have dissolved, add additional distilled water to the bottle untilthe water level is approximately 1 inch from the top. Stopper and shake thoroughly to mix.This sodium hydroxide solution is the titrant for the analyses to follow. Keep the bottle tightly stoppered when not actually in use (to avoid exposure of the NaOH to the air). Set up buret in the buret clamp. See Figure 26-1. Rinse and fill the buret with the sodium hydroxide solution just prepared.B.Standardization of the Sodium Hydroxide SolutionClean and dry a small beaker. Take the beaker to the oven that contains the primary standard grade potassium hydrogen phthalate (KHP).Using tongs or a towel to protect your hands, remove the bottle of KHP from the oven, and pour afew grams into the beaker. If you pour too much, do not return the KHP to the bottle. Return the bottle of KHP to the oven, and take the beaker containing KHP back to your lab bench. Cover thebeaker with a watch glass.Allow the KHP to cool to room temperature. While the KHP is cooling, clean three 250-ml Erlenmeyer flasks with soap and water. Rinse the Erlenmeyer flasks with several small portions of distilled water.Label the Erlenmeyer flasks as 1,2, and 3.Figure 2. Set up for titration. The buret must be scrupulously clean, such that water runs down the interior walls in sheets and does not bead up anywhere. A funnel should be used when filling the buret, and the buret should be below eye level when the titrant is added to it.When the KHP has completely cooled, weigh three samples of KHP between 0.6 and 0.8 g, one for each of the Erlenmeyer flasks. Record the exact weight of each KHP sample at least to the nearest milligram, preferably to the nearest 0.1 mg (if an analytical balance is available). Be certain not to confuse the samples.At your lab bench, add 100 ml of water to KHP sample 1.
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- Winter '15
- Chemistry, Sodium hydroxide, Erlenmeyer flask, KHP