Equations Aluminium hydroxide

Calculating the bicarbonate concentrations with (3), it is possible to plot the measured average pH values of Table 2 against the calculated loglHCOs ]. The result is shown in Fig. 5a. For pH >5.5 a linear relationship, very close to that reported in the literature, can be observed (pH = loglHCOa ] + 11.2). However, for acid lakes the calculated bicarbonate concentrations seem to be too low. It is reported that at pH<6 the release of metals from soils or sediments as a consequence of weathering processes becomes more and more important. Consequently aluminium hydroxides can influence alkalinity. In [18] the equation for calculating alkalinity was modified as follows ... 

Preparation of an Aluminium Hydroxide Sol by Peptization, Prepare 100 g of a 10% aluminium chloride solution. Add an ammonia solution to it up to complete precipitation of aluminium hydroxide. Write the equation of the reaction. Wash the precipitate twO or three times with water by decantation, and then on a filter in a Buchner funnel. When the precipitate becomes viscid, transfer it into a large beaker and add 50 ml of distilled water. Boil the contents... 

Prepare aluminium hydroxide (what methods can be used for this purpose ). Wash the precipitate by decantation and treat it with (a) a sulphuric acid solution, (b) an excess of a sodium hydroxide solution, and (c) an excess of an ammonia solution. What do. you observe Write the equations of the reactions. How can solid sodium aluminate be prepared ... 

Discussion of Experiment 169.—When sodium hydroxide or potassium hydroxide is first added to a solution of a compound of aluminium, aluminium hydroxide is formed. The simplest equation for this reaction is —... 

Pour one-third of the contents of the test tube into each of two other test tubes, to one of which add an excess of hydrochloric acid. (3) What occurred (4) Write an equation for the reaction. (5) As what kind of a compound does aluminium hydroxide act ... 

Write two ionic equations to show that aluminium hydroxide is amphoteric. 

With the aid of two equations, show how aluminium hydroxide exhibits amphoteric behaviour. 

Coagulants are often added in conjunction with lime to increase the settling rate of calcium carbonate and magnesium hydroxide. Most of these coagulants are acidic in nature and react with the alkalinity of the water. Commonly used coagulants include aluminium sulphate (alum), sodium aluminate, ferric sulphate and ferrous sulphate (Table 6.8). Alum reacts with natural alkalinity in water to form aluminium hydroxide floe (Equations 2.5—2.8) [14]. About 1 ppmofalumdecreaseswater alkahnity by 0.5 ppm and produces 0.44 ppm of CO2 ... 

Von Weimarn experimented mainly on the formation of precipitates of slightly insoluble inorganic compounds like silver sulphate, barium sulphate, aluminium hydroxide, which he prepared by double decomposition of other salts, added together under varying conditions of concentration and temperature and with or without addition of other liquids, like alkohol, to influence solubility and medium conditions. The essential result of his experiments may be cast into the form of the following equation ... 

Write balanced equations for the following reactions, a Iron reacts with hydrochloric acid to form iron(ll) chloride, FeCl, and hydrogen, b Aluminium hydroxide, AlfOEIlg, decomposes on heating to form aluminium oxide, AljOj, and water, c Elexane, CgH, burns in oxygen to form carbon dioxide and water. 

A second general feature of aluminium chemistry is the tendency of the element to form the oxide or hydroxide compounds. This is especially clear when comparisons are made with, say, sodium. The tendency is made evident in the insolubility of A1(0H)3 in water and its solubility in alkali, in the way in which the non-existent carbonate decomposes to AI2O3, and in the acidity of the aqueous ion (Equation 9.19). Again, unlike NaCl, AICI3 fumes in moist air because hydrogen chloride gas is formed along with aluminium hydroxide ... 

Kaolinite can react with water to give aluminium hydroxide (gibbsite) and hydrated silicic acid. The aluminium hydroxide dissolves in the presence of hydrogen ions, as shown in Equation 6.2 ... 

Why is potassium aluminium sulphate not soluble in benzene A compound M has the composition C = 50.0% H=12.5%o A1 = 37.5%. 0.360 g of M reacts with an excess of water to evolve 0.336 1 of gas N and leave a white gelatinous precipitate R. R dissolves in aqueous sodium hydroxide and in hydrochloric acid. 20 cm of N require 40 cm of oxygen for complete combustion, carbon dioxide and water being the only products. Identify compounds N and R, suggest a structural formula for M, and write an equation for the reaction of M with water. (All gas volumes were measured at s.t.p.)... 

The data given in Tables 1.9 and 1.10 have been based on the assumption that metal cations are the sole species formed, but at higher pH values oxides, hydrated oxides or hydroxides may be formed, and the relevant half reactions will be of the form shown in equations 2(a) and 2(b) (Table 1.7). In these circumstances the a + will be governed by the solubility product of the solid compound and the pH of the solution. At higher pH values the solid compound may become unstable with respect to metal anions (equations 3(a) and 3(b), Table 1.7), and metals like aluminium, zinc, tin and lead, which form amphoteric oxides, corrode in alkaline solutions. It is evident, therefore, that the equilibrium between a metal and an aqueous solution is far more complex than that illustrated in Tables 1.9 and 1.10. Nevertheless, as will be discussed subsequently, a similar thermodynamic approach is possible. 

One advantage of this method of preparation of hydroxides is that formation in a neutral solution renders unnecessary careful washing to free from excess of alkali, which is generally needed in ordinary precipitation processes. Further, there is no risk that excess of alkali will redissolve the hydroxide or oxide of metals such as zinc or aluminium, and the electrolyte is re-formed continuously so that it lasts indefinitely, and hence the cost of alkali is avoided. The reaction in the case of copper is represented by the equation CuCl2 + 2NaOH = Cu(OH)2 + 2NaCl. 

Some oxides and hydroxides are able to react with both acids and bases, thereby functioning as both bases and acids, respectively. Water is probably the most common example, but in this section we consider the amphoteric nature of metal oxides and hydroxides. Aluminium oxide, AI2O3, reacts with acids (equation 6.39) and with hydroxide ion (equation 6.40). 

Directions To 10 c.c. of aluminium sulphate solution in a test tube add 10 drops of sodium hydroxide solution. (1) Describe the appearance of the precipitate. (2) Write the equation for its formation. 

Destabilisation may be achieved by the enmeshment of the colloid in a precipitate. In this process a metal salt such as aluminium sulphate (alum) or ferric chloride, is added to the water forming positively charged species in the typical pH range of 6 - 7 for clarification. The hydrolysis reaction produces an insoluble gelatinous hydroxide according to the following equations ... 

The most commonly used coagulating agents are ferric and aluminium salts (e.g. ferric chloride, FeCla, ferric sulfate, Fe2(S04)3 and alum, Al2(S04)3 I4H2O), which are precipitated as the hydroxides, (e.g., equations 28.1, 28.2). Both reactions generate mineral acids which may need to be neutralised by the addition of an alkali to produce the required pH. 

According to Davenport et al. [39], when a piece of aluminium is immersed in a bath containing Ce ions at a neutral pH, the cerium will deposit as Ce with a long exposure time (5 days), probably following equation 9.9. Nevertheless, when time of exposure is increased to 7 days, the deposit having Ce was oxidised to Ce", probably indicating that reaction 9.13 took place indicating that reactions 9.14 and 9.15 are hindered due to the effect of the cerium hydroxide layer on the cathodic reduction reactions. 

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