Acids, Bases And Salts

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Introduction to Acids, Bases and Salts. lemon Definition Nutrition Uses Facts Britannica.

Classification of matter. Based on a) composition – elements, compounds and mixtures b) state – solids, liquids and gases c) solubility – suspensions, colloids and solutions Types of mixtures – homogeneous and heterogeneous Types of compounds – covalent and ionic.

What Is an Acid and a Base?. Logo, company name Description automatically generated.

Ionisable and non-ionisable compounds. An ionisable compound when dissolved in water or in its molten state, dissociates into ions almost entirely. Example: NaCl, HCl, KOH, etc. A non-ionisable compound does not dissociate into ions when dissolved in water or in its molten state. Example: glucose, acetone, etc..

Acids and Bases. An acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance. A base is a molecule or ion able to accept a hydrogen ion from an acid. Acidic substances are usually identified by their sour taste..

Arrhenius theory of acids and bases. OH OH. Arrhenius acid – when dissolved in water, dissociates to give H + (aq) or H 3 O + ion. Arrhenius base – when dissolved in water, dissociates to give OH − ion..

Examples. Acids Hydrochloric acid (HCl) Sulphuric acid (H 2 SO 4 ) Nitric acid (HNO 3 ) Bases Sodium hydroxide (NaOH) Potassium hydroxide (KOH) Calcium hydroxide (Ca(OH) 2 ).

Bronsted Lowry theory. A Bronsted acid is an H + (aq) ion donor. A Bronsted base is an H + (aq) ion acceptor. Example In the reaction: HCl (aq) + NH 3 (aq) → NH + 4 (aq) + Cl − (aq) HCl – Bronsted acid and Cl − : its conjugate acid NH 3 – Bronsted base and NH + 4 : its conjugate acid.

Physical test. a. Taste An acid tastes sour whereas a base tastes bitter. The method of taste is not advised as an acid or a base could be contaminated or corrosive. Example: The flavours of curd, lemon juice, orange juice, and vinegar are all sour. Because they contain acids, these compounds have a sour flavour. Baking soda has a sour flavour. It’s an example of a foundation..

b. Effect on indicators by acids and bases. An indicator is a chemical substance which shows a change in its physical properties, mainly colour or odour when brought in contact with an acid or a base. Below mentioned are commonly used indicators and the different colours they exhibit: a) Litmus In a neutral solution – purple In acidic solution – red In basic solution – blue Litmus is also available as strips of paper in two variants – red litmus and blue litmus. An acid turns a moist blue litmus paper to red. A base turns a moist red litmus paper to blue..

b) Methyl orange In a neutral solution – orange In acidic solution – red In basic solution – yellow c) Phenolphthalein In a neutral solution – colourless In acidic solution – remains colourless In basic solution – pink.

Acid-Base Reactions. A neutralisation reaction occurs when an acid reacts with a base. A salt and water are the end products of this reaction. An acid–base neutralisation reaction is formulated as a double-replacement reaction in this standard approach..

Reactions of acids and bases. Formulae written on a blackboard.

a) Reaction of acids and bases with metals. Acids, in general, react with metals to produce salt and hydrogen gas. Bases, in general, do not react with metals and do not produce hydrogen gas. Acid + active metal → salt + hydrogen + heat 2HCl + Mg → MgCl 2 + H 2 (↑) Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen Base + metal → salt + hydrogen + heat 2NaOH + Zn → Na 2 ZnO 2 + H 2 (↑) Sodium hydroxide + Zinc → Sodium zincate + Hydrogen A more reactive metal displaces the less reactive metal from its base. 2Na + Mg (OH) 2 → 2NaOH + Mg Sodium + Magnesium hydroxide → Sodium hydroxide + Magnesium.

b) Reaction of acids with metal carbonates and bicarbonates.

c) Reaction of Acid with Base. 1. Reaction of metal oxides and hydroxides with acids Metal oxides or metal hydroxides are basic in nature. Acid + base → salt + water + heat H 2 SO 4 + MgO → MgSO 4 + H 2 O 2HCl + Mg (OH) 2 → MgCl 2 + 2H 2 O 2. Reaction of non-metal oxides with bases Non-metal oxides are acidic in nature Base + Nonmetal oxide → salt + water + heat 2NaOH + CO 2 → Na 2 CO 3 + H 2 O.

3.Reaction of acids and base. A very common acid is hydrochloric acid. The reaction between strong acid says hydrochloric acid and strong base say sodium hydroxide forms salt and water. The complete chemical equation is shown below. HCl (strong acid) + NaOH (strong base) → NaCl (salt) + H2O (water).

abstract. Water. Acids and bases in water When added to water, acids and bases dissociate into their respective ions and help in conducting electricity..

Difference between a base and an alkali. Base: Bases undergo neutralisation reaction with acids. They are comprised of metal oxides, metal hydroxides, metal carbonates and metal bicarbonates. Most of them are insoluble in water. Alkali: An alkali is an aqueous solution of a base, (mainly metallic hydroxides). It dissolves in water and dissociates to give OH − ion. All alkalis are bases, but not all bases are alkalis..

Hydronium ion. Hydronium ion is formed when a hydrogen ion accepts a lone pair of electrons from the oxygen atom of a water molecule, forming a coordinate covalent bond..

Dilution. Using the dilution factor to calculate dilutions Hemocytometer.

Strength of acids and bases. Strong acid or base : When all molecules of a given amount of an acid or a base dissociate completely in water to furnish their respective ions, H + (aq) for acid and OH − (aq) for base). Weak acid or base: When only a few of the molecules of a given amount of an acid or a base dissociate in water to furnish their respective ions, H + (aq) for acid and OH − (aq) for base)..

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abstract. Dilute acid: contains a smaller number of H + (aq) ions per unit volume. Concentrated acid: contains a greater number of H + (aq) ions per unit volume..

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Universal indicator. A universal indicator has a pH range from 0 to 14 that indicates the acidity or alkalinity of a solution. A neutral solution has pH=7 pH pH=−log 10 [H + ] In pure water, [H + ]=[OH − ]=10 −7 mol/L. Hence, the pH of pure water is 7. The pH scale ranges from 0 to 14. If pH < 7 → acidic solution If pH > 7→ basic solution.

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Importance of pH in everyday life. 1. pH sensitivity of plants and animals Plants and animals are sensitive to pH. Crucial life processes such as digestion of food, functions of enzymes and hormones happen at a certain pH value. 2. pH of a soil The pH of a soil optimal for the growth of plants or crops is 6.5 to 7.0. 3. pH in the digestive system The process of digestion happens at a specific pH in our stomach which is 1.5 to 4. The pH of the interaction of enzymes, while food is being digested, is influenced by HCl in our stomach. 4. pH in tooth decay Tooth decay happens when the teeth are exposed to an acidic environment of pH 5.5 and below. 5. pH of self-defence by animals and plants Acidic substances are used by animals and plants as a self-defence mechanism. For example, bee and plants like nettle secrete a highly acidic substance for self-defence. These secreted acidic substances have a specific pH..

Salts. A salt is a combination of an anion of an acid and a cation of a base. Examples – KCl, NaNO 3 ,CaSO 4 , etc. Salts are usually prepared by the neutralisation reaction of an acid and a base..

Common salt Sodium Chloride (NaCl) is referred to as common salt because it’s used all over the world for cooking. Family of salts Salts having the same cation or anion belong to the same family. For example, NaCl, KCl, LiCl..

pH of salts. A salt of a strong acid and a strong base will be neutral in nature. pH = 7 (approx.). A salt of a weak acid and a strong base will be basic in nature. pH > 7. A salt of a strong acid and a weak base will be acidic in nature. pH < 7. The pH of a salt of a weak acid and a weak base is determined by conducting a pH test..

Chemicals from common salt. Flask. Sodium chloride is a common salt. NaCl is its molecular formula. The fundamental element in our meals is sodium chloride. It is used in our food as a flavour enhancer as well as a preservative. From common salt, we may make the following four compounds. Sodium hydroxide or lye or caustic soda Baking soda or sodium hydrogen carbonate or sodium bicarbonate Washing soda or sodium carbonate decahydrate Bleaching powder or calcium hypochlorite.

Preparation of Sodium hydroxide. The strong base sodium hydroxide is a common and useful one. Preparing a solution of sodium hydroxide (NaOH) in water requires extra caution because the exothermic reaction releases a lot of heat. It’s possible that the solution will spatter or boil. Here’s how to manufacture a sodium hydroxide solution safely, as well as recipes for a variety of NaOH strengths. Chemical formula – NaOH Also known as – caustic soda.

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Preparation (Chlor-alkali process):. Beaker. Electrolysis of brine (solution of common salt, NaCl) is carried out. At anode: Cl 2 is released At cathode: H 2 is released Sodium hydroxide remains in the solution..

Bleaching powder. Bleaching powder is soluble in water and is used as a bleaching agent in textile industries. It is also used as an oxidizing agent and a disinfectant in many industries. It should also be noted that bleaching powder is synthesized by the reacting chlorine gas on dry slaked lime i.e. Ca(OH)2. Chemical formula – Ca(OCl)Cl or CaOCl 2 Preparation – Ca(OH) 2 (aq)+Cl 2 (g)→CaOCl 2 (aq)+H 2 O(l) On interaction with water – bleaching powder releases chlorine which is responsible for bleaching action..

Uses of Bleaching Powder. It is used for bleaching dirty clothes in the laundry, as a bleaching agent for cotton and linen in the textile industry. It is a strong oxidizing agent, hence used as an oxidizer in many industries. It is used as a disinfectant which is used for disinfecting water to make potable water..

Baking soda. Sodium bicarbonate, also known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO 3 and the IUPAC designation sodium hydrogencarbonate. A sodium cation (Na + ) and a bicarbonate anion (HCO 3 ) combine to form this salt. Sodium bicarbonate is a white, crystalline substance that is commonly found as a fine powder. It tastes slightly salty and alkaline, like washing soda (sodium carbonate). Chemical name – Sodium hydrogen carbonate Chemical formula – NaHCO 3.

Preparation (Solvay process):. a. Limestone is heated: CaCO 3 →CaO+CO 2 b. CO 2 is passed through a concentrated solution of sodium chloride and ammonia: NaCl(aq)+NH 3 (g)+CO 2 (g)+H 2 O(l)→NaHCO 3 (aq)+NH 4 Cl(aq) Uses: Reduces the acidity in the stomach Acts as an antacid which is used to treat stomach upset and indigestion Used in the process of washing as a water softener.

Washing soda. Chemical name – Sodium hydrogen carbonate Chemical formula – NaHCO 3 Preparation (Solvay process) – a. Limestone is heated: CaCO 3 → CaO + CO 2 b. CO 2 is passed through a concentrated solution of sodium chloride and ammonia: NaCl(aq) + NH 3 (g) + CO 2 (g) + H 2 O(l) → NaHCO 3 (aq) + NH 4 Cl(aq) Uses 1. In glass, soap and paper industries 2. Softening of water 3. Domestic cleaner.

Crystals of salts. Certain salts form crystals by combining with a definite proportion of water. The water that combines with the salt is called water of crystallisation. The process by which a solid forms, in which the atoms or molecules are strongly arranged into a structure known as a crystal, is known as crystallisation. Precipitation from a solution, freezing, and, more rarely, direct deposition from a gas are some of the ways crystals form. Example- Table salt (sodium chloride or halite crystals), sugar (sucrose), and snowflakes are examples of common materials that form crystals. Many gemstones, such as quartz and diamond, are crystals..

Plaster of paris. Plaster of Paris is a widely used chemical compound that is extensively used in sculpting materials and gauze bandages. Plaster of Paris is a white powdery chemical compound that is hydrated calcium sulphate that is usually obtained by calcining gypsum. While we have seen many applications of this material in our everyday lives, if we try to understand its chemistry, we will find that it is a white powdery chemical compound that is hydrated calcium sulphate that is usually obtained by calcining gypsum. To put it another way, Plaster of Paris is often manufactured of heated gypsum at a high temperature. Gypsum plaster is another name for plaster of Paris. Plaster of Paris is expressed as CaSO 4 . ½ H 2 O in chemical formula. Gypsum, CaSO 4 .2H 2 O (s) on heating at 100°C (373K) gives CaSO 4 . ½ H 2 O and 3/2 H 2 O CaSO 4 . ½ H 2 O is plaster of paris. CaSO 4 . ½ H 2 O means two formula units of CaSO 4 share one molecule of water. Uses – cast for healing fractures..

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