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" sound on burning.
- Nitric acid is an oxidizing agent so it oxidizes hydrogen to \[{{H}_{2}}O\] & itself get reduced.
But \[Mg\And Mn\] react with very dilute \[HN{{O}_{3}}\] to produce hydrogen gas.
\[Mg+2HN{{O}_{3}}\to Mg{{(N{{O}_{3}})}_{2}}+{{H}_{2}}\,(1%)\]
- Metal oxides are basic in nature. They react with acids to form salt and water.
\[{{K}_{2}}O+2HCl\to 2KCl+{{H}_{2}}O\]
\[MgO+{{H}_{2}}S{{O}_{4}}\to MgS{{O}_{4}}+\,{{H}_{2}}O\]
- Metal hydroxides react with acids to form salt and water.
\[2\,KOH+{{H}_{2}}S{{O}_{4}}\to {{K}_{2}}S{{O}_{4}}+2{{H}_{2}}O\]
\[NaOH+HCl\to MgS{{O}_{4}}+{{H}_{2}}O\]
- Acids reacts with metal carbonates and hydrogen carbonates to form salt, water and liberate carbon dioxide gas.
\[2NaH\,C{{O}_{3}}+{{H}_{2}}S{{O}_{4}}\to N{{a}_{2}}S{{O}_{4}}+2{{H}_{2}}O+2C{{O}_{2}}\]
\[Zn\,C{{O}_{3}}+2HCl\to ZN\,C{{l}_{2}}+{{H}_{2}}O+C{{O}_{2}}\]
Carbon dioxide gas when passed through line water, turns it to milky due to the formation of calcium carbonate.
\[Ca{{(OH)}_{2}}+C{{O}_{2}}\to CaC{{O}_{3}}+{{H}_{2}}O\]
Acids react with sulphites and hydrogen sulphites to form salt, water and sulphurdioxide
\[{{K}_{2}}S{{O}_{3}}+{{H}_{2}}S{{O}_{4}}\to {{K}_{2}}S{{O}_{4}}+{{H}_{2}}O+S{{O}_{2}}\]
\[NaHS{{O}_{3}}+NaCl\to NaCl+{{H}_{2}}O+S{{O}_{2}}\]
Sulphur dioxide gas also turn lime water milky when passed through it, but is not permanent.
- Acids react with metal sulphides to form salt and hydrogen sulphide gas. |
\[MgS+{{H}_{2}}S{{O}_{4}}\to MgS{{O}_{4}}+{{H}_{2}}S\]
\[FeS+2HCl\to FeC{{l}_{2}}+{{H}_{2}}S\]
Hydrogen sulphide gas smells like rotten egg.
Uses of Some Common Acids
- Acetic acid - For Cooking
- Oxalic acid - For removing stain off
- Citric acid - Food preservative
- Tartaric acid - For baking power
- Boric acid - For washing eyes
- Carbonic acid - In soft drinks
- Preparation of Bases
Preparation of Bases
- By direct combination of metal and oxygen
\[2Mg+{{O}_{2}}\to 2MgO\]
\[4Na+{{O}_{2}}\to 2N{{a}_{2}}O\]
- By dissolving basic oxides in water
\[N{{a}_{2}}O+{{H}_{2}}O\to 2NaOH\]
\[MgO+{{H}_{2}}O\to Mg{{(OH)}_{2}}\]
- By reacting active metals with water
\[2K+2{{H}_{2}}O\to 2KOH+{{H}_{2}}\]
\[Ca+2{{H}_{2}}O\to Ca{{(OH)}_{2}}+{{H}_{2}}\]
- By thermal decomposition of metal
\[ZnC{{O}_{3}}\to ZnO+C{{O}_{2}}\]
\[CuC{{O}_{3}}\to CuO+C{{O}_{2}}\]
Sodium and potassium carbonates do not give this reaction
- By thermal decomposition of metal nitrates
\[2Al(N{{O}_{3}})\to A{{l}_{2}}{{O}_{3}}+6N{{O}_{2}}+3{{O}_{2}}\]
\[CuC{{l}_{2}}+NaOH\to NaCl+Cu{{(OH)}_{2}}\]
- By treating aqueous salt solution of certain metal with strong base.
\[ZnS{{O}_{4}}+2KOH\to {{K}_{2}}S{{O}_{4}}+Zn{{(OH)}_{2}}\]
\[CuC{{l}_{2}}+NaOH\to NaCl+Cu{{(OH)}_{2}}\]
Properties of Base
They have bitter taste
They are soapy 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.
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.
Litmus: It is very common indicator present in the labs in the form of litmus solution or litmus paper.
Acids turn blue litmus red and bases turn red litmus blue.
Methyl Orange: It is an orange coloured synthetic indicator, which gives pink colour with acids and yellow colours with base.
Phenolphthalein: It is a colour less indicator which, shows no change in acidic solution but turn pink in basic solution.
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:
Methods of Preventing Corrosion
The spoiling of metals due to corrosion can be prevented by
The process of coating iron with zinc is called:
(a) Electroplating
(b) Polishing
(c) Galvanization
(d) Reduction
(e) None of these
Answer: (c)
Explanation
Galvanization is the process of coating iron with zinc in order to prevent its rusting.
Types of Chemical Reactions
The chemical reactions are of following types
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.
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.
Steps to be followed for balancing chemical equation
What will happen when a piece of iron metal is placed is copper sulphate solution?
(a) Physical change
(b) A chemical reaction
(c) Evolution of gas
(d) Heat will be evolved.
(e) None of these
Answer: (b)
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.
The chemical changes are the outcome of chemical reactions. So the chemical reaction can be defined as the change of one or more substance into other substances having different chemical composition and properties.
For example. Hydrogen (gas) + Chlorine (g) \[\to \] Hydrogen chloride (g)
\[{{H}_{2}}+C{{l}_{2}}\to 2HCl\]
Carbon (s) + Oxygen (g) \[\to \] Carbon dioxide
\[{{C}_{2}}+2{{O}_{2}}\to 2C{{O}_{2}}\]
Characteristics of Chemical Reactions
Some of the important characteristics of chemical reactions are:
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 have the potential to be safer and generate less radioactive waste than fission.
These reactions appear potentially viable, though technically quite difficult and have yet to be created on a scale that could be used in a functional power plant. Fusion power has been under intense theoretical and experimental investigation since the 1950s. Nuclear power plants convert the energy released from the nucleus of an atom, typically via nuclear fission.
Disposal of nuclear waste is often said to be the Achilles' heel of the industry. Presently, waste is mainly stored at individual reactor sites and there are over 430 locations around the world where radioactive material continues to accumulate. Experts agree that centralized underground repositories which are well-managed, guarded, and monitored, would be a vast improvement. There is an "international consensus on the advisability of storing nuclear waste in deep underground repositories", but no country in the world has yet opened such a site.
Which one among the following is a non renewable sources of energy?
(a) Wind Energy
(b) Solar Energy
(c) Biomass
(d) Petrol
(e) None of these
Answer: (d)
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 earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming, if widely deployed in place of fossil fuels. Geothermal electric plants were traditionally built exclusively on the edges of tectonic plates where high temperature geothermal resources are available near the surface. The thermal efficiency of geothermal electric plants is low, around 10-23%, because geothermal fluids do not reach the high temperatures of steam from boilers.
The laws of thermodynamics limit the efficiency of heat engines in extracting useful energy. Exhaust heat is wasted, unless it can be used directly and locally, for example in. greenhouses, timber mills, and district heating. Geothermal power requires no fuel except for pumps, and is therefore immune to fuel cost fluctuations, but capital costs are significant. Drilling accounts for over half the costs, and exploration of deep resources entails significant risks. A typical extraction and injection wells in Nevada can support 4.5 megawatts (MW) and costs about $10 million to drill, with a 20% failure rate. Geothermal power is considered to be sustainable because any projected heat extraction is small compared to the Earth's heat content.
The Earth has an internal heat content of 1031 joules (3-1015 TW-hr). About 20% of this is residual heat from planetary accretion, and the remainder is attributed to higher radioactive decay rates that existed in the past. 
