Sometimes it is sufficient to show only that certain ions or elements are present in a sample, and in this case a chemist will perform a qualitative test. Summary table for Week 3. After the vacuum filtration process the content becomes clear. Keep the crystals from different crops and syntheses separate. The solution was allowed to cool then acidified slowly with constant stirring using 45mL of 3M sulfuric acid. Allow it to begin to cool while you prepare an ice bath, an ice-water mixture in a 400-mL beaker. Does this sample contain potassium? Dilute to the mark and mix thoroughly.
The product of this reaction is aluminum sulfate and water. September 8,2010 — September 10,2010 c. These hazards are generally associated with heating things e. Obtain the mass of the crucible, its cover, and the alum to the nearest milligram and record this in your notebook. Dilute all the solutions to the mark by adding distilled water and mix thoroughly. While the mixture is heating, clean and dry exterior only your volumetric flasks. The beaker is placed in an ice bath to cool the solution, filling the beaker three fourths full with ice and cold water.
The filter and precipitate was then transferred to an evaporating dish and allowed to dry in an oven. If the alum is dry, the filter paper will separate from the crystals and you can remove the filter paper. The water can violently leave the alum at this point, if it is heated too strongly. The final qualitative test was the red lake test for aluminum. After 10 minutes the whole solution turns clear. Week 2: A tared blue weighing boat was placed onto the balance and the balanced was zeroed. Slowly and carefully add 25 mL of the 1.
Advanced Chemistry with Vernier See other experiments from the lab book. Contaminants may react with one of the reactants, leading to a decrease in the desired reaction. The description of a chemical reaction consists of a series of steps: 1 carrying out the reaction, 2 isolating the product s , 3 purifying the product s , 4 and characterizing the product s and determining its their purity. Undissolved solids were removed and discarded through vacuum filtration. Calculate a percent error for the class average and for your result. To find the percent sulfate, an amount of barium nitrate is allowed to react with the sample to precipitate all of the sulfate in the compound as barium sulfate. The solution is then transferred to a clean 250 mL beaker, and the suction flask is rinsed with 10 mL distilled water to insure all the remaining solution is transferred to the clean beaker.
The flask may be heated gently in order to facilitate dissolution. Quantitative Determination of Waters of Hydration Before beginning this section be sure that your alum sample is powdered and that you have weighed your alum sample! After stirring for several minutes, crystals began to form. From the class data, calculate the average percent water by weight in alum, the standard deviation of the data and determine the confidence limits at 95% confidence. A small amount of alum was dissolved in a test tube in minimum amount of water. Also place a test tube containing 15 mL of 95% ethanol in the ice bath. If some water remained in the product that was assumed to be anhydrous, then when the mole ratio was calculated, it would have seemed as if the moles of water were smaller.
Lab report on synthesis of Alum using Aluminum. After cooling, the precipitate was massed and the percent sulfate present in the alum was compared to the value calculated from its formula. We put the tube in a water bath with a temperature probe and waited until the powder became clear. Carefully scrape any alum that adheres to the side of the Büchner funnel onto the watch glass. Alum is an ionic compound, which means its melting and boiling points are likely to be too high to be measured conveniently.
After cooling, the mass of the anhydrous alum and the water driven off were calculated and compared to the accepted value of alum. Avoid inhaling the gas evolved during this reaction. One of these influences is the obtainment of impurities into the sample being tested. This means that it contains a salt and water combined in definite proportion. The foiled weighed more than 0. Synthesis of a Hydrate: In the first trial we obtained a percent yield of 65. Remember to include the confidence interval on the class average % Al by mass in alum.
Set on burner, heat with cover loose for 5 minutes. The amount that we get back after the experiment 7. Do not dip the pipet into the filtered solution! Note: you will not use the second, taped filter flask shown as a trap in the lab handout. To identify a compound with certainty, experiments have to be conducted in order to verify these properties. During this hour, the qualitative tests were completed. Therefore, one can assume that in a 100 g sample of alum, there would be 29.
Impurities in the reactants also cause errors. Do not use the water aspirators to dry the crystals. Quantitatively transfer, as your instructor will demonstrate, to a small beaker and add distilled water to bring the volume to about 15 mL. In the first week we are less concerned with precision than we are in the third week. Add about 10 mL of distilled water and swirl to dissolve the AlCl 3· 6H 2O. Synthesis of a Hydrate: The purpose of this experiment is to become familiar with the formation of hydrates and using sequential reactions. A way to prevent this type of error would be to heat the alum thoroughly, either by heating more vigorously or for a longer period of time.
Aluminium foil may be taken instead of scrap aluminium. Synthesis of a Hydrate: Trial Mass of empty container Mass of container and crystals Mass of crystals Percent yield 1 11. Also, some of the crystals may have gotten lost while being transferred from the beaker, to the aspirator, and then to another beaker to be measured. The vacuum was turned off. Procedure Clean a small piece of scrap aluminium with steel wool and cut it into very small pieces. Each crucible was weighted and the mass of each was recorded. The filter paper was rinsed in the sink and discarded into the trash can.