Then again, while leaving behind as much solid as possible, transfer as much liquid as possible into a pressure filtration assembly (p. 68 lab text) and filter the liquid into a clean, dry, tared 25 mL Erlenmeyer flask (tared = weighed empty). Be sure that the filter assembly is resting in the flask prior to transferring the liquid, as some liquid will filter through immediately. The filtration apparatus is made by pushing the micro Buchner funnel (polyethylene frit in place - no filter paper) into the end of a plastic pipet which has had the tip cut off and which has had a small hole cut into the squeeze bulb). Allow most of the liquid to filter by gravity, then, while holding your thumb over the hole in the squeeze bulb, gently apply pressure to complete the filtration. Care must be taken when squeezing the pipet bulb on the filter pipet.
In this step, as we watched the chemical reaction with the solids, we noticed a thinning in the substance. Also, the solids became lighter and moved to the top. When stirred, the solution began to turn green and then back to light blue, where copper began in the end of the first step. A combination reaction took place, and the balanced equation is: CuOs+H2SO4aq→CuSO4aq+H2O(I) Following this step, step 5 began, in which we added 300 mg of zinc to the solution. Once the zinc was added slowly to the solution, a gas was released and the solution began to change colors.
Add 1 mL of deionized water to the small test tube containing the precipitate and mix it and centrifuge it for 60 seconds. Then, add the supernatant into the boiling test tube and repeat this step one more time with another 1 mL of deionized water. Acquire a pair of metal test tube holders and heat the boiling test tube to evaporate the water for 15 minutes. Let is cool after and weigh it. Then, calculate a percent yield of zinc iodide and write a balanced chemical equation and determine the limiting
Repeat the titration until there are two titres within 0.1cm3 of each other. Record results in a suitable table. Results: Rough Titre: 7.653 First Run: 6.553 Second Run: 6.453 Third Run: 6.553 Calculations: During the titration, iron(II) ions are oxidised to iron(III) ions and manganate(VII) ions are reduced to manganese(II) ions. The equation is as follows: 5Fe2+(aq) + MnO4-(aq) + 8H+(aq) ? 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) The above equation shows that one mole of manganate(VII) ions reacts with 5 moles of iron(II) ions in acid solution.
This technique prevents the product to contact other reactants, and leave the heating environment which might cause side reactions. The removal of the product also helps to shift the equilibrium position of the incomplete reaction to the right hand side, and prevents backwards reaction, resulting in an increased yield of products. This experiment also introduces the idea of azeotrope. An azeotrope is a mixture of two or more pure compounds in such a ratio that its composition cannot be changed by simple distillation. This is because when an azeotrope is boiled, the resulting vapour has the same ratio of constituents as the original mixture of liquids.
In step 4 there wasn’t any change because we just decanted it, which means we used water to rinse it. 5.) In step 5 we added 15ml of (6M) H2SO4. When we added the H2SO4 the solution turned back to a translucent blue liquid. 6.)
Lab 4: Determination of Percent by Mass of the Composition in a Mixture by Gravimetric Analysis Introduction Thermal gravimetric analysis is used to determine the percent by mass is used to determine the percent by mass of a component in a mixture. When a mixture is heated to an appropriately high temperature, one component in the mixture decomposes to form a gaseous compound. The mass of this particular component is related to the mass of the gaseous compound. In this experiment, the percent by mass of sodium hydrogen carbonate (NaHCO3) and potassium chloride (KCl) in a mixture will be determined. Experimental First, we weighed 2 samples, each has 1 gram of NaHCO3-KCl mixture Second, we put the samples in 2 crucibles (A and B) and weighed them.
Why is this necessary? Obtain an appropriate amount of 5.00 M NaCl and fill your 25 mL buret. Pipet a 20.00 mL aliquot of 0.100 M acetic acid solution into a 100 mL beaker, add a magnetic stirring bar, and then set up the titration apparatus as indicated in Figure 1. Record the initial pH and then begin titrating. You will titrate in 0.25 mL intervals for the first 2 ml and then in 1 mL intervals until a total of 6 mL of 5.00 M NaCl has been delivered.
Record several points of pH and NaOH added (especially near equivalence point) to be use later to prepare a titration curve. Observations and Results Part I: Solution | pH | 0.1 M HCl | .70 | 0.1 M NaOH | 13.30 | Part II: Volume of 0.1 M NaOH at equivalence point: 35mL pH at equivalence point: 11.45 Molarity of the Unknown Acid A (HCl): 2.0 x 10-4 Discussion In this lab, we found out that water self ionizes itself into hydrogen ion and hydroxide ion naturally to a very small extent. An indicator, in an acid base reaction, is a substance whose color changes over a particular pH range. Phenolphthalein is an example of an indicator which changes from colorless to pink as pH goes from 8 to 10. We plotted the pH against the amount of base added producing a
The following data were obtained when a sample of barium chloride hydrate was analyzed as described in the Procedure section. Calculate (a) the mass of the hydrate, (b) the mass of water lost during heating, and (c) the percent water in the hydrate. Mass of empty test tube 18.42 g Mass of test tube and hydrate (before heating) 20.75 g Mass of test tube and anhydrous salt (after heating) 20.41 g. Mass of the Hydrate is 2.33g. Loss (H2O) is 0.34g. Percent H2O in Hydrate is equal 0.34/2.33=14.6% 3.