Title 3. ACIDS, BASES AND SALTS _CW_WS -1 TO 2-VOL-4_PG.pdf ✅

Olympiad Text Book 91 Narayana Group of Schools VII– Chemistry (Vol – IV) Olympiad Class Work Book CONCEPT FLOW CHART
VII–Chemistry (Vol–IV) 92 Narayana Group of Schools Olympiad Class Work Book ARRHENIUS [1859 – 1927] ARRHENIUS : “ARRHENIUS”(1859-1927) was a swedish physicists and physical chemist known for his theory of electrolytic dissociation and his model of the green house effect. At the age of Three, Arrhenius taught himself to read without the encouragement of his parents ,and he watching his father’s addition of numbers in his account books,become an arithmetical prodigy. In 1903 he was awarded the nobel prize for chemistry. ACIDS,BASES AND SALTS
Olympiad Text Book 93 Narayana Group of Schools VII– Chemistry (Vol – IV) Olympiad Class Work Book ACIDS BASES AND SALTS Introduction: Every chemical in this world is either acidic, basic or neutral. In nature Curd, Vinegar, Tamarind and Lemon juice etc., all have sour taste. Green mangoes, Tomatoes, Karvina (corinda) and unripened grapes also taste sour. Many fruits (specially citrus fruits) and some vegetables are sour in taste because acidic nature which is present naturally in them. On the other hand, there are some substances such as Washing soda, Lime and materials like soap whose solutions have a soapy touch and bitter taste. These materials are either bases or alkalies. An acid and a base react together forming water and a new compound known as salt. Acids: The term acid is derived from the Latin word ‘acidus’ meaning sour. Large number of fruits and vegetables have a sour taste. The sour taste of a Lemon is due to Citric acid, the sour taste of Grapes or Tamarind is due to Tartaric acid. Lavoisier first prepared acids by heating non-metals in Oxygen and then dissolving the oxides in water. Definition: A substance which dissolves in water to furnish H+ ions is called an acid. (Or) Acids are defined as compounds which contain one or more Hydrogen atoms and when dissolved in water produce Hydronium ions (H3O+ ), the only positively charged ions At first the acid molecule furnishes Hydrogen ion (or proton) i.e. H+ in an aqueous solution. H O2 HCl H Cl      But this H+ ion cannot exist independently. Therefore it combines with a water molecule to form Hydronium ion (H3O+ ). This hydrated ion can now exist independently in solution. + + H + H O H O 2 3       H O2 2 H SO 2H SO 2 4 4 H O2 HNO H NO 3 3         CH COOH H CH COO 3 3  
VII–Chemistry (Vol–IV) 94 Narayana Group of Schools Olympiad Class Work Book Basicity of an acid: The number of Hydrogen ions (H+ ) furnished by one molecule of an acid, on dissolving in water is called Basicity of an acid. i) Mono basic acids: Acids which on ionisation in water produce one Hydrogen ion (H  ) or Hydronium ion ( H O3  ) per molecule of the acid are known as monobasic acids Example: Hydrochloric acid Basicity is 1.    HCl H Cl   Some other examples are: HBr, HI, HNO , CH COOH, H PO 3 3 3 2 ii) Dibasic acids: Acids which on ionisation in Water produce two Hydrogen ions (H  ) or Hydronium ions ( H O3  ) per molecule of the acid are known as Dibasic acids. Example:      2 H SO 2H SO 2 4 4 Sulphuric acid basicity= 2 Some other examples: H C O , H SO , H CO , H PO 2 2 4 2 3 2 3 2 3 iii) Tribasic acids: Acids which on ionisation in Water produce three Hydrogen ions (H  ) or Hydronium ions ( H O3  ) per molecule of the acid are called Tribasic acids. Example: H PO 3 4      3 H PO 3H PO , 3 4 4 Basicity = 3 Other example: Citric acid (C6 H8 O7 ), basicity is 3. Note: Basicity of Silicic acid [H4SiO4 ] is 4 Classification of Acids on the basis of Origin: On the basis of their origin the acids have been classified into two broad classes i) Organic acids ii) Inorganic acids i) Organic acids: Acids which are obtained from natural organic matter such as plants and animals are called Organic acids. Some organic acids Organic acid Source Oxalic acid Spinach, Tomato Lactic acid Sour milk