BBC - Intermediate 2 Bitesize Chemistry - Acids and Bases : Revision
Key words: phosphate adsorption, metal hydroxides, metal oxides. Résumé: L' élimination du .. also mixed into the water to create additional pores after the. Since hydroxide ion is the strongest base that can persist in water, the oxide ion those metal oxides of the nonacidic and feebly acidic cation dissolve in water. these oxides do not significantly alter the pH of the water, they are still bases. This can also be proven by the litmus paper test where metal oxides when reacting with water will form strong bases and turn red litmus paper to blue. On the.
The oxides of nonacidic cations are so water reactive that they are seldom seen.
These oxides cannot be prepared by dehydrating the hydroxide at high temperature. The oxides of feebly acidic cations are more common. Lime, CaO is an example. Lime can be prepared comercially by the thermal decomposition of limestone. The oxides of feebly acidic cations react exothermically with water producing the hydroxide. The hydroxides of feebly acidic cations are not deliquescent.
The oxides of weakly acidic cations and moderately acidic cations are insoluble in water. These oxides do not introduce significant amounts of O2- ion into the solution so hydroxide ions are not produced. Although these oxides do not significantly alter the pH of the water, they are still bases and neutralize strong acids. Many of these oxides dissolve in water to give the oxo anion in which the element has the same oxidation number as the oxide.
BBC - GCSE Bitesize: Bases and acids
The oxide will be soluble if its reaction with water produces a strong or very strong acid because these acids ionize completely shifting the equilibrium toward dissolution. The pattern is less clear for other oxides.
Non-metal oxide acidity is defined in terms of the acidic solutions formed in reactions with water—for example, sulfur trioxide reacts with water to forms sulfuric acid. They will all, however, react with bases such as sodium hydroxide to form salts such as sodium sulfate as explored in detail below. Sodium Oxide Sodium oxide is a simple strongly basic oxide. It is basic because it contains the oxide ion, O2- which is a very strong base with a high tendency to combine with hydrogen ions.
Sodium oxide reacts exothermically with cold water to produce sodium hydroxide solution. A concentrated solution of sodium oxide in water will have pH As a strong base, sodium oxide also reacts with acids. For example, it reacts with dilute hydrochloric acid to produce sodium chloride solution.
However, it is not as strongly basic as sodium oxide because the oxide ions are not as weakly-bound.
Bases and acids
Because of the higher charge on the metal, more energy is required to break this association. At first glance, magnesium oxide powder does not appear to react with water. However, the pH of the resulting solution is about 9, indicating that hydroxide ions have been produced.
In fact, some magnesium hydroxide is formed in the reaction, but as the species is almost insoluble, few hydroxide ions actually dissolve. The reaction is shown below: Magnesium oxide reacts with acids as predicted for a simple metal oxide.
For example, it reacts with warm dilute hydrochloric acid to give magnesium chloride solution.
One of those forms is very unreactive known chemically as alpha-Al2O3 and is produced at high temperatures. The following reactions concern the more reactive forms of the molecule.
Acid-base Behavior of the Oxides
Aluminium oxide is amphoteric. It has reactions as both a base and an acid. Aluminum oxide is insoluble in water and does not react like sodium oxide and magnesium oxide. The oxide ions are held too strongly in the solid lattice to react with the water.
Periodic Trends and Oxides
Aluminum oxide contains oxide ions, and thus reacts with acids in the same way sodium or magnesium oxides do. Aluminum oxide reacts with hot dilute hydrochloric acid to give aluminum chloride solution.
Aluminum oxide also displays acidic properties, as shown in its reactions with bases such as sodium hydroxide. Various aluminates compounds in which the aluminum is a component in a negative ion exist, which is possible because aluminum can form covalent bonds with oxygen.
This is possible because the electronegativity difference between aluminum and oxygen is small, unlike the difference between sodium and oxygen, for example electronegativity increases across a period Aluminum oxide reacts with hot, concentrated sodium hydroxide solution to produce a colorless solution of sodium tetrahydroxoaluminate: Therefore, because silicon dioxide does not contain oxide ions, it has no basic properties.
In fact, it is very weakly acidic, reacting with strong bases.
Silicon dioxide does not react with water, due to the thermodynamic difficulty of breaking up its network covalent structure. Silicon dioxide reacts with hot, concentrated sodium hydroxide solution, forming a colorless solution of sodium silicate: