10th Class

         Preparation of Acids  

• By direct combination of a non metal with hydrogen

e.g.   \[{{H}_{2}}+\,C{{l}_{2}}\,\to 2HCl;\,\,{{H}_{2}}+S\to {{H}_{2}}S;\,\,{{H}_{2}}+B{{r}_{2}}\to 2HBr\]

• By reaction between salt and the less concentrated acid

e.g. \[KCl+{{H}_{2}}S{{O}_{4}}\to {{H}_{2}}S{{O}_{4}}+HCl;\,\,NaCl+{{H}_{2}}S{{O}_{4}}\to NaHO{{S}_{4}}+HCl\]

• By action of concentrated nitric acid on non metals.

e.g.   \[S+6HN{{O}_{3}}(con)\to {{H}_{2}}S{{O}_{4}}+2{{H}_{2}}O+6N{{O}_{2}}\]

• By dissolving non-metal oxides in water

e.g. \[S{{O}_{3}}+{{H}_{2}}O\to {{H}_{2}}S{{O}_{4}};\,{{N}_{2}}{{O}_{5}}+{{H}_{2}}O\to 2NH{{O}_{3}};\,C{{O}_{2}}+{{H}_{2}}O\to \,{{H}_{2}}C{{O}_{3}}\]

• By action of dilute mineral acids on salts such as chlorides, carbonates sulphates etc.

e.g. \[{{K}_{2}}{{O}_{3}}+{{H}_{2}}S{{O}_{4}}\,(dil)\to {{K}_{2}}S{{O}_{4}}+{{H}_{2}}S{{O}_{4}};\,FeS+{{H}_{2}}S{{O}_{4}}\,(dil)\to FeS{{O}_{4}}+{{H}_{2}}S\]            Properties of Acids

They have sour taste

They turns blue litmus red

III. Dilute mineral acids reacts with metals, above hydrogen in the activity series to liberate hydrogen gas. \[2Na+2HCl\,(dil)\to 2NaCl+{{H}_{2}}\] \[Zn+{{H}_{2}}S{{O}_{4}}(dil)\to ZnS{{O}_{4}}+{{H}_{2}}\] (4) Reaction of Na, K, Ca with acid is explosive. (5) Hydrogen gas evolved produces "POP" more...

          Classification of Acids                   Classification on the Basis of the Concentration of Acid The concentration of acid is the amount of acid dissolved in water. On the basis of concentration acids are of two types:                 Concentrated Acid A concentrated acid has relatively high percentage of hydrogen ions in the aqueous solution. e.g. Concentrated hydrochloric acid, concentrated sulphuric acid etc.              Dilute Acid A dilute acid has relatively low percentage of hydrogen ions in water. e.g. dilute hydrochloric acid, dilute sulphuric acid etc.                Classification on the Basis of more...

       Introduction   The chemicals which we come across in our daily life can be categorized as acids, bases or salts. For example the common salt is sodium chloride and the detergent powder that is used for washing clothes is another salt of sodium i.e. sodium carbonate. The vinegar used in pickles is an acid i.e. acetic acid, the citrus fruits also contains the acid. The solution which is used for white washing contains calcium hydroxide which is a base. The soaps which we use is made from the base sodium chloride. Now in order to identify whether a given substance is an acid or a base, an indicators is used.             Indicators Those chemical substance which change their colour when they are put in acid or base are known as indicators. The three more...

          Effect of Oxidation Reactions in Daily Life   Many oxidation reactions take place in our daily life. Some of them are useful while others are harmful. The two such common oxidation reactions are:

• Corrosion

It is the degradation of metals due to their reaction with oxygen. Carbon-dioxide, water etc.

• Rusting

It is a common type of corrosion. It is formed when iron comes in contact with moist air. As a result of corrosion a reddish brown layer of ferric oxide is formed which is called is called rust. \[4F{{e}_{(s)}}+3{{O}_{2(g)}}+2n{{H}_{2}}O\to 2F{{e}_{2}}{{O}_{3}}\cdot n{{H}_{2}}{{O}_{(S)}}\]  (Rust) Copper articles when left out in moist air gets coated with a green layer. This is another example of corrosion where copper gets coated with basic copper carbonate layer. \[2\,C{{u}_{(s)}}+C{{O}_{2}}_{(g)}+{{O}_{2}}_{(g)}\to CuC{{O}_{3}}\cdot Cu{{(OH)}_{2}}\]

• Effects of Corrosion

It weakens more...

       Types of Chemical Reactions   The chemical reactions are of following types

• Combination Reaction
• Decomposition Reaction
• Displacement Reaction
• Double Displacement Reaction
• Precipitation Reaction
• Redox Reaction

               Combination Reaction Combination reactions are those chemical reaction in which two or more elements or compounds combine together to form a single compound. e.g. Hydrogen and nitrogen reacts to form ammonia \[3{{H}_{2}}(g)+{{N}_{2}}(g)\to 2N{{H}_{3}}(g)\] e.g. Burning of carbon \[{{C}_{(s)}}+{{O}_{2}}(g)\to C{{O}_{2}}(g)\] For white washing solution of calcium hydroxide (slaked lime is used). It combines with carbon dioxide in air to form a layer of calcium carbonate which gives a shiny appearance to the surface of wall.                Decomposition Reaction Those reactions in which single more...

       Balancing of Chemical Equations   The chemical equations must be written in accordance with the law of conservation of mass. The law of conservation of mass states that: "The matter can neither be created nor destroyed". OR "In a chemical reaction, the total mass of reactants is equal to the total mass of products".                    We always have to represent a chemical reaction by balancing the equation. "A balanced chemical equation is the one in which the atoms of each element must be equal on both sides of the equation". \[{{N}_{2}}+3{{H}_{2}}\to 2N{{H}_{3}}\] In the above equation we see that the number of atoms of each elements is same on both side of the reaction and hence it can be said as balanced. To make the atoms of each element equal on both sides of the equation is called balancing of chemical equation.                                more...

       Chemical equations   Symbolic representation of chemical reaction with the help of symbols and formula is called a chemical reactions.       Sodium hydroxide reacts with hydrochloric acid to form sodium chloride salt and water. So, the above statement can be written in the form of chemical equation as below: \[NaOH+HCl\to NaCl+{{H}_{2}}O\]

       Introduction   In this chapter we will study about chemical reactions and equations, balancing of equations, types of chemical reactions, effects of oxidation in daily life and many more.            Chemical Reactions Let us consider the two process:

• Dissolution of sugar in water and
• Cooking of food.

  In the first process the properties of both sugar and water are present in the solution and no new chemical compound is formed, so it is a physical change. On the other hand in the second process that is cooking of food, the ingredients loose their nature and form a new substance with different properties is formed so this is called a chemical change.   The chemical changes are the outcome of chemical reactions. So more...

     Nuclear Energy   Nuclear potential energy is the potential energy of the particles inside an atomic nucleus. The nuclear particles are bound together by the strong nuclear force. Weak nuclear forces, provide the potential energy for certain kinds of radioactive decay, such as beta decay. Nuclear particles like protons and neutrons are not destroyed in fission and fusion processes, but collections of them have less mass than if they were individually free, and this mass difference is liberated as heat and radiation in nuclear reactions. The energy from the Sun is an example of this form of energy conversion. In the Sun, the process of hydrogen fusion converts about 4 million tones of solar matter per second into electromagnetic energy, which is radiated into space. Nuclear power provides about 6% of the world's energy and 13-14% of the world's electricity. Nuclear fusion reactions more...

       Geothermal Energy   Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet, from radioactive decay of minerals, from volcanic activity, and from solar energy absorbed at the surface. The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heats from the core to the surface. Geothermal power is cost-effective, reliable, sustainable, and environmentally friendly, but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have dramatically expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the more...