4. Action on litmus paper? Turn blue litmus to red. Acid has a pH range which >7 Some of the weaker acids, however, for example carbonic acid, are so feebly acidic that they can only turn litmus to claret color. Acids contain combined hydrogen. When a sample of zinc, a fairly reactive metal, is dropped into a test tube containing a acid such as HCl m a reaction occurs. The bubbling in the tube indicates that a gas is released. When we test this gas by inserting a burning splint into the test tube, the gas burst into flame and produces a small popping sound. This is the characteristic test for hydrogen gas. In general, when certain acids react with metals, hydrogen gas is released. Metal + acid metal salt + hydrogen Reaction with carbonates Form salts, water and carbon dioxide gas. Example: Na 2 CO 3 (s) + 2HCl 2NaCl (aq) + CO 2 (g) + H 2 O Properties Of Acids: Taste? Sour. This is true of the three common mineral acid, sulphuric acids, hydrochloric acids, nitric acids and others. The sour taste of many unripe fruits, lemons and sour milk is cause by the acids in them. Corrosive action Most people connect the term acid with the idea of a corrosive, “burning” liquid. Two of the commonest acids- sulphuric acid and nitric acid- are actually corrosive liquids. Acids are not, however, generally corrosive and most of them are solids. Acids release hydrogen in water solutions. When an acid dissolves in water, the acid ionizes, releasing both hydrogen ions and ions of a non-metal or non metallic polyatomic ion. Thus, when hydrochloric acid is dissolved in water, the acid ionizes, forming hydrogen ions and chloride ions, as shown in the following equation: HCl (aq) H + (aq) + Cl 1- (aq) other examples: H z SO 4 (aq) 2H + (aq) + SO 4 2- (aq) H 3 PO 4 (aq) 3H + (aq) + PO 4 3- (aq) * Thus acids are defined as substances that release hydrogen ions in solution. It is these H + (aq) are responsible for the properties of acids. Reaction with bases: Form salts and water. Another word: neutralization. Ionic equation: H + + OH - H 2 O Example: HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)
5. The reactions of the three common inorganic acids with various metals.
16. What is salt? Many chemical compounds may classified as salt. The most familiar to all of us is the table salt. In general, salts are ionic compounds that are composed of metallic ions and non-metallic ions. For example, sodium chloride is composed of metallic sodium ions and non metallic chloride ions. Salts can be considered to be formed by the reaction of an acid with a base. Salts are classified into neutral, basic or acidic according to the effect they have on pH when dissolved in water. Strong acid + strong base neutral solution Weak acid+ strong base base solution Strong acid +weak base acidic solution