Objective The ability to analyze a substance and determine properties of the substance is an important skill for AP Chemistry students. Major concepts for the “Analysis of Alum” laboratory are percent composition, water of hydration, and molecular formula. They will be used in three different experiments to determine the melting point of alum, the mole ratio of hydrated water to anhydrous alum, and percent of sulfate ion contained in alum. The values acquired in the lab should be close to the calculated values of 92.5 ˚F, 12 moles of water to 1 mole of alum, and 59%, respectively. Before beginning the experiment, it is important to review skills and concepts with Pre-Lab questions. 1. When measuring a melting point, why is it necessary to …show more content…
Especially with big quantities of a substance, the melting point tends to be a range of values rather than just one value. This is because all the substance will not melt at once; it takes some time to melt at its estimated melting point. However, the hot plate will continue to increase the temperature, even when the substance is at its melting point. Thus, a more accurate range of temperatures will be acquired if the substance is heated slowly. 2. Washing soda is a hydrated compound whose formula can be written Na¬2CO3•xH2O, where x is the number of moles of H¬2O per mole of Na¬2CO3. When a 2.123 g sample of washing soda was heated at 130 ˚C, all of the water of hydration was lost, leaving 0.787 g of anhydrous sodium carbonate. Calculate the value of …show more content…
Melting Point Determination of Alum 1. 0.5 g of dry alum was crushed with the mortar and pestle, and then the crushed alum was packed to the bottom the capillary tube. The alum measured about 0.5 cm from the bottom of the tube. Then the tube was fastened to the thermometer with the rubber band, and the thermometer was fastened to the ring stand with the universal clamp. 2. The bottom of the capillary tube and the thermometer were submerged in a beaker of heating water. The water was stirred occasionally and heated very quickly. However, when the water reached 80 ˚C it was heated very slowly in order to not pass the melting point. 3. The temperature when alum melted was recorded in the data table. Part 2. Determination of the Water of Hydration in Alum Crystals 1. The Bunsen burner was set up under a ring stand fitted with a ring clamp. It was adjusted to be 1 cm above the Bunsen burner, and the clay pipestem triangle was placed on the clamp. 2. The crucible and cover were placed on the triangle, and they were heated until they turned red hot. Afterwards, they were removed from the fire with the tongs and placed on the wire gauze to cool for ten minutes. Then, the mass of the crucible and cover was measured and recorded in the data
The purpose for this lab was to use aluminum from a soda can to form a chemical compound known as hydrated potassium aluminum sulfate. In the lab aluminum waste were dissolved in KOH or potassium sulfide to form a complex alum. The solution was then filtered through gravity filtration to remove any solid material. 25 mLs of sulfuric acid was then added while gently boiling the solution resulting in crystals forming after cooling in an ice bath. The product was then collected and filter through vacuum filtration. Lastly, crystals were collected and weighed on a scale.
It was learned that changing the volume of the same substance will never change the boiling point of the substance. However having two different substances with the same volume will result in two different boiling points. The purpose of this lab was to determine if changing the volume of a substance will change the boiling point. This is useful to know in real life because if someone wanted to boil water to make pasta and did not know how much water to
We were then to make a base solution of 0.7 M NaOH. In order to standardize
The equation shows how 1 mol of Na2CO3 reacts with 1 mol of H2SO4, so
In my experiment, I will use an overall volume of 50 cm³ of 2moles of
frac{E}{N} = frac{2 pi na {hbar}^2}{m} Bigg( 1 + frac{128}{15sqrt{pi}}sqrt{na^3} + frac{8(4pi-3sqrt{3})}{3}na^3 (ln(na^3)+c) + ... Bigg)
PART I. INTRODUCTION The molarity of an unknown acid will be determined using a method called "titration". Titration is the process of the gradual addition of a solution of known concentration to a second solution until the solute in the second solution has completely reacted. A solution of known concentration used in a titration is called a standard solution. In today's experiment, NaOH, a base, is the standard solution. Sodium hydroxide will be added to an unknown acid. The unknown acid and the base reacts and forms salt and water. This type of reaction is called neutralization: NaOH + HA ---> H2O + NaA HA is an abbreviation for an unknown acid. A substance called an indicator is added to show the end of the titration.
I ended up starting at 6.4 and use all of it up to 49.0. To make silver nitrate, we used (0.5 mol) *(.250 dm squared) which equals .125, then times .125 by the molar mass which is 169.82 to get 21.2275 grams. From that point, we were able to make the solution of silver nitrate.
11.) Subtract the mass of the evaporating dish from the mass of the evaporating dish and it's contents. Multiply that number by 10 to get the solubilty in grams per 100 cm3 of water.
be the volume of Nitric Acid and water but only to total 15cm³ so the
between BaCl and BaSO, and that AW of 1 mol of BaSO = 233.404, so we
our total volume to be 55 cm³, 5 cm³ of that hydrochloric acid, so the
According to the conductometric titration, the concentration of Ba(OH)2 (aq) was 0.196 M. Calculations based on gravimetric analysis revealed a concentration of 0.0669 M. Evidently, there is a high degree of imprecision between the values determined by each technique. It appears however that the gravimetric analysis was more accurate. The standard deviation for BaSO4 mass was 0.035 and the confidence interval was ±0.0256 g. This illustrates that there is 90% certainty that the actual mass of the BaSO4 precipitate was within 0.0256 g of the calculated mean (0.156 g). It should be noted that an outlier (1.45 g precipitate) was removed from the gravimetric analysis calculations due to being 9.29 times greater than the average. The standard deviation for end point volume – the basis of calculations for the conductometric titration – was 6.616. The confidence interval was ±5.443 mL. The much larger confidence interval for end point volume illustrates a higher degree of uncertainty regarding the precision of this measurement. For this reason, it appears that gravimetric analyses are more suitable for determining saturated solution concentration. This has importance in research where the solubility product (Ksp) needs to be determined or when predictions need to made regarding whether a precipitate will form. One of the principle reasons why conductometric titration
Since I am making a 0.1 Mconcentration, I will need 0.001 moles of each sugar.
of Copper Sulphate. To do this I plan to work out the amount of water