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Explain the following terms with one example each. (a) Corrosion (b) Rancidity

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  Ques 20 : Explain the following terms with one example each.   (a) Corrosion (b) Rancidity Ans 20: (a) Corrosion: Corrosion is defined as a process where materials, usually metals, deteriorate as a result of a chemical reaction with air, moisture, chemicals, etc. For example, iron, in the presence of moisture, reacts with oxygen to form hydrated iron oxide.  (b) Rancidity: The process of oxidation of fats and oils that can be easily noticed by the change in taste and smell is known as rancidity. For example, the taste and smell of butter changes when kept for long. Rancidity can be avoided by:   1. Storing food in air tight containers 2. Storing food in refrigerators 3. Adding antioxidants 4. Storing food in an environment of nitrogen.  «« Previous question                     Chapter1 Additional Solutions »»
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Oil and fat containing food items are flushed with nitrogen. Why?

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Ques 19 : Oil and fat containing food items are flushed with nitrogen. Why? Ans 19 : Nitrogen is an inert gas and does not easily react with these substances. On the   other hand, oxygen reacts with food substances and makes them rancid. Thus, bags  used in packing food items are flushed with nitrogen gas to remove oxygen inside  t he pack. When oxygen is not present inside the pack, rancidity of oil and fat containing food items is avoided. «« Previous question              Next question »»
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Why do we apply paint on iron articles?

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Ques 18 : Why do we apply paint on iron articles? Ans 18 : Iron articles are painted because it prevents them from rusting. When painted,   the contact of iron articles from moisture and air is cut off. Hence, rusting is prevented their presence is essential for rusting to take place.    «« Previous question              Next question »»
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A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

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Ques 17 : : A shiny brown-coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.    Ans 17: ‘X’ is copper (Cu) and the black-coloured compound formed is copper oxide (Cu O).  «« Previous question              Next question »»
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Current Electricity Notes Unit 3 Class 12 || Unit 3 || Physics || Class 12 || Chapter 3 Notes Class 12 ||

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                            Electric current The rate of flow of charges through any area of cross-section of a wire is called electric current flowing through it.                   Electric current (I) = q / t.  Its SI unit is ampere (A). The conventional direction of electric current is the direction of motion of positive charge. The current is the same for all cross-sections of a conductor of non-uniform cross-section. Similar to the water flow, charge flows faster where the conductor is smaller in cross-section and slower where the conductor is larger in cross-section, so that charge rate remains unchanged. If a charge q revolves in a circle with frequency f, the equivalent current,                             i = q f  (In a metallic conductor current flows due to motion of free electrons w...
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Electric Charges and Fields || Electrostatics Notes || Physics || Class 12 || Chapter 1 Notes Class 12 ||

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                            Charge Charge is that property of an object by virtue of which it apply electrostatic force of interaction on other objects. Charges are of two types (i) Positive charge (+ve)  (ii) Negative charge (-ve)  Like charges repel and unlike charges attract each other.               Quantization of Charge Charge on any object can be an integer multiple of a smallest charge (e).                     Q = ± n e where, n = 1, 2, 3,……. and e = 1.6 * 10-19 C.                   Conservation of Charge Charge can neither be created nor be destroyed. but can be transferral from one object to another object. Recently a new particle has been discovered called ‘Quark’. It contains charge ± e / 3, ± 2e / 3. [The protons and neutrons are combination of other entities called ...
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Let A be the set of all students of a boys school. Show that the relation R in A given by R = {(a, b: a is sister of b} is the empty relation and R' = {(a, b: the difference between heights of a and b is less than 3 meters} is the universal relation.

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Example 1 : Let A be the set of all students of a boys school. Show that the relation R in A given by R = {(a, b: a is sister of b} is the empty relation and R' = {(a, b: the difference between heights of a and b is less than 3 meters} is the universal relation.  Ans : Since, the school is boys school, no student of the school can be sister of any student of the school. Hence, R = ∅,  showing that R is the empty relation. It is also obvious that the difference between heights of any two students of the school has to less than 3 metres. This shows that R' = A X A is the universal relation.
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QUANTUM NUMBERS (Principal, Azimuthal, Magnetic and Spin)

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                  QUANTUM NUMBERS  Orbitals represent regions in the space around the nucleus where the probability of finding the electron is maximum. A large number of electron orbitals are possible in atom. These can be distinguished by their size, shape and orientation of the orbitals. To describe each electron in an atom in different orbitals, we need a set of three numbers known as quantum numbers. These are designated as n, l and m. In addition to these three numbers another quantum number is also needed which specifies the spin of the electron. These four numbers are called quantum numbers. These are discussed below: 1. Principal quantum number (n) :  This quantum number determines the main energy shell or level in which the electron is present. It is denoted by n. It can have whole number values starting from 1 such as n = 1, 2, 3, 4 ... This quantum number also identifies as shell. The shell with n 1 is called the first sh...
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Diagonal Relationship between Beryllium and Aluminium || Relation between Beryllium and Aluminium

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  Diagonal Relationship between Beryllium and Aluminium The ionic radius of Beryllium (Be 2+) is estimated to be nearly 31 pm; the charge/radius ratio Or e/m ratio is nearly the same as that of the Al 3+ ion. Hence beryllium resembles aluminium in these ways. Some of the similarities are given below: » Like Aluminium, Beryllium(be) is not readily attacked by acids H+ donor because of the formation of an oxide film on the surface of the metal by reacting with oxygen, i.e. they are rendered passive by nitric acid. » Beryllium hydroxide[[Be(OH)4]2] dissolves in excess of alkali to give a beryllate ion, [ Be(OH)4]2– just as aluminium hydroxide[Al(OH)3] gives aluminate ion, [Al(OH)4] » The chlorides of metals beryllium and aluminium have Cl– bridged chloride structure in vapour phase. Both the chlorides are soluble in organic solvents and are strong as Lewis acids They are used as Friedel Craft catalysts. » Beryllium(Be) and aluminium(Al) ions have strong tendency to form complexes, (Be...
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Math question

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A tower, x metre, has a flagstaff at its top. The tower and flagstaff subtends equal angles at a point distant y metre from the foot of the tower. Then find the length of the flagstaff ( in metre). 
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Solar System, Planets, Moons, Asteroid Belt,Kuiper Belt and Oort Cloud, Comets and Meteoroids

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 The solar system consists of the Sun, which is a star at its center, and all the celestial bodies bound by its gravitational pull. These bodies include planets, moons, asteroids, comets, and other objects. Key Components of the Solar System: The Sun : The Sun is the center of the solar system and contains about 99.86% of its mass. It is a star primarily composed of hydrogen and helium, providing the heat and light that sustains life on Earth. Planets : There are eight recognized planets in the solar system: Mercury : The closest planet to the Sun, known for extreme temperature variations and no atmosphere. Venus : Similar in size to Earth but with a thick, toxic atmosphere and surface temperatures hot enough to melt lead. Earth : The third planet from the Sun, the only known planet to support life, with water and a breathable atmosphere. Mars : Known as the Red Planet, it has a cold, dry surface and signs of past water. Jupiter : The largest planet, a gas giant, w...
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