Preparation and Reactions of Boric Acid
To prepare boric acid from sodium deteriorate (borax) To carry out tests on the prepared sample of boric acid To study the physical and chemical properties of boric acid Introduction: Boron is an element in the p-block of the periodic table. It has the electron configuration of 1s22s22p1 and is in group 3 or coup 13 (PUPAS classification). In nature, it consists of two isotopes BIB (19. 6%) and BIB (80. 4%). Boron is bonded to the oxygen in nature. The important sources of Boron are borax and kerning.
Boron sides and their derivatives are technologically important and are relatively inexpensive to produce. Boron oxides is very difficult to crystallite and normally exists in a glassy state (d=l . CACM-1). Molten boron oxide has a high melting point of 450 degree Celsius that is readily dissolves metal oxides to form colored borate glasses as one of the main commercial uses of boric oxide. Particularly, borosilicate glasses find wide applications in glassblowing and the production of glass objects. On top of the boric acid, it is also known as hydrogen borate as a weak monobasic
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Lewis acid. At room temperature, it exists as white powder or colorless crystals with a chemical formula of HOBBS or B(OH)3. Apparatus and materials: ;Sodium deteriorate ;Concentrated hydrochloric acid ;Concentrated sulfuric acid ;Methyl red indicator ;Imitation ;Beaker ;Methanol ;Distilled water ;Electric heater ;Test tube ;Test tube rack ;Glass rod ;Suction funnel ;Suction pump ;Filter flask ;Filter paper ;Spatula ;Watch glass ;Splint Procedures: 1 . About log of sodium deteriorate (borax) is dissolved in CACM of water in a beaker. 2.
The mixture is boiled and CACM of concentrated hydrochloric is added into the solution. 3. The beaker is immersed into a container with ice and water to cool down the temperature. 4. After the solution is cooled down, the boric acid is crystallized out by using the Boucher funnel, 2 layers of filter papers, suction pump and a filtering flask. 5. The remaining crystals in the beaker and on the glass rod are washed well with ice-cold water for a few times and filtered off with the Boucher funnel. 6. The yield is left aside to be dried and the weight is measured and recorded.
Test 1 1. A little boric acid is inserted into a test tube. 2. Small amount of distilled water is added to dissolve the acid in the test tube. 3. A drop of methyl red indicator is added. 4. Test tube is labeled as A. 5. Steps 1 to 3 are repeated again by replacing the acid with the imitation and the test tube is labeled as B. 6. Half of each solution in test tube A and B are mixed in a test tube labeled as C. 7. All results and observation are recorded. -rest 2 1. A small amount of boric acid crystals is inserted into a Tyrant boiling tube. 2.
A little ethanol is added into the boiling tube Just to cover the acid. 3. Some concentrated sulfuric acid is then added into the tube. 4. The boiling tube is held by a test tube holder and heated on a Bunsen burner. 5. The vapor produced is ignited by using a burning wooden splinter. 6. All observations are recorded. Discussion: First and foremost, we managed to yield 4. Egg of HOBBS. According to our calculation, the theoretical mass that we are supposed to obtain is 6. Egg. This means that our percentage of yield is 74. 64%. According to Vogue’s Textbook of
Practical Organic Chemistry, yields around 100% are called quantitative, whereas yields above 70% are good. This means that our team did quite a great Job. Boric acid is a Lewis acid that is able to interact with the water molecules to give out hydrogen ions and dehydrogenation ion in the solution. In test 1, the methyl red indicator is used to determine the acidity of the each solution in different test tubes. The indicator can show the pH range at around 4. 4 – 6. 2. At pH 4. 4, the solution with the indicator will appear to be in red in color and whereas at pH 6. , it will show allow. On test tube A, solution turns from colorless to pink color. This shows that boric acid is a relatively weak acid with pH around 4-5. Next on test tube B, the methyl red indicator is added into a imitation solution. The color of the solution seemed to remain unchanged. It is colorless. In fact, the solution is supposed to change from colorless to yellow. Perhaps, we accidentally made some mistakes by adding the wrong reactant in the experiment or we were a bit of too rush deciding the color of the solution without looking at it carefully.
Thirdly, when we mix both he solutions from A and B, an intense pink solution is formed. This means that a stronger acid is formed. It can be simply explained by the stronger acid complex formed in between imitation and boric acid. The pH is less than 4 for sure. According to the test 2 results, a beautiful green flame is formed when we ignite the vapor with a burning wooden splinter. By mixing the alcohol (methanol) and acid (conch HOSTS) will create ester (CHI)BIBB. An alcohol flame itself is usually, ordinarily colorless. The presence of the green in the flame is indicating the ester formed contains boron element.
A strong acid like concentrated sulfuric acid is needed to propionate the HOBBS and this will create the electroplate which attacks the O atom of the methanol. Without the existence of a strong acid, an intense green flame might not be formed. This is because ester may not formed and even if it is formed, it will exist in equilibrium with the alcohol & boric acid. Thus, making the green flame not really intense. There are a few precautionary steps that should be taken during this experiment. Firstly, suction pump used in test 1 is powerful and thus, 2 layers of filter papers are seed to cover the holes of the Boucher funnel.
From our experience, the suction pump will cause the filter paper to be torn if only a piece of filter paper is used. Furthermore, we shall always pour the solution slowly on the rod, so that the solution will flow slowly without causing any wastage. By using this method, we can make sure the crystals are accumulated in the middle of the filter paper and it eases our Job to take out the filter paper from the funnel. On top of the safety, all acids are corrosive. In this experiment, we use concentrated hydrochloric acid and concentrated elliptic acid.
We shall wear gloves and handle them with extra care to prevent and avoid any accident to occur. In addition, a tyrant boiling tube is used instead of a test tube in test 2 (flame test). A boiling tube can withstand strong heat without breakage. Test 2 (flame test) has to be carried out in the fume hood as the vapor released from the boiling tube is toxic. Therefore, we shall remain our distance with the vapor, although the green flame is beautiful. Last but not least, we shall discard the excess boric acid into the waste bottle instead of basin as to prevent water pollution.