Chemistry

An atom or group of atoms which bears charge and behaves as single unit during chemical reaction is called radical. Eg. SO4--, Ca++ etc. Depending on charges present, radicals are classified as below:- Electropositive Radical (Basic Radical) (Cation):- These radicals possess positive charge and collect at cathode during electrolysis. Eg. NH4+, Ca++, Zn++ etc. Electronegative Radicals (Acid Radical/Anion):- These radicals possess negative charge and collect at anode during electrolysis. Eg. SO4--, Cl-, NO3- etc. Depending on constituent atoms radicals are classified as below:- i] Simple Radical This type of radicals contains only one type of atoms that can be one…

Valency: Valency is the combining capacity of an element with other elements. In electronic concept, valency is the number of electrons gained or lost or shared by an atom of an element during chemical reaction. Valency of an element depends on the number of valence electrons present in an element. Variable Valency: Some elements can show two or more than two different valencies while forming different compounds. These different valencies are due to the participation of different number of electrons while forming compounds. Such different valencies are called variable valencies.  

Symbol: Symbol is the abbreviation which is given to represent full name for elements. Eg. Hydrogen – H Sodium – Na Gold - Au Carbon – C Calcium – Ca Cadium – Cd Significance of Symbol: A symbol has qualitative as well as quantitative significance. Qualitative Significance: 1. Qualitatively symbol helps us to know the name of element. Quantitative Significance: 1. Quantitatively symbol of an element represents an atom of that element. Molecular Formula: The symbolic representation of a molecule of substance is called molecular formula. Molecular formula shows the exact number and types of atoms present in a molecule.…

Equivalent weight of Element: Equivalent weight of an element is defined as the number of parts by weight of that element which can combine or displace directly or indirectly 1.008 parts by weight of hydrogen or 8 parts by weight of oxygen or 35.5 parts by weight of chlorine or their equivalent. Mathematically, i.e., E= A/V Gram Equivalent Weight: When Equivalent weight of substance is expressed in gram, then it is called gram equivalent weight. 2×1.008 parts by wt. of hydrogen is displaced by 24 parts by weight of mg. 1.008 parts by wt. of hydrogen is displaced by 24/2…

In this method small amount of weighed volatile liquid is converted into vapour. This vapour is collected and its volume is converted into STP or NTP. Now the weight of same volume of hydrogen at STP is calculated. Finally vapour density is calculated as: After calculating V.D., molecular weight is calculated as:- Molecular Weight = 2×Vapour Density. Observation and Calculation, Wt. of Liquid = W1 gm Volume of vapour = V1 ml Pressure of vapour = (P1) = p - f Room Temperature = T1 At STP, Pressure (P2) = 760mmHg Temperature (T2) = 273 K Volume (V2) = ?…

In 1811 Amadeo Avogadro proposed his hypothesis. According to his hypothesis under the similar condition of temperature and pressure equal volume of all gases contain the same number of molecules. Application of Avogadro's Hypothesis:- i] To establish the relation between molecular weight and vapour density or,      Prove that: Molecular Weight = 2 × Vapour Density                                            Mol. Wt. = 2 × V.D. Vapour density is the ratio of weight of certain volume of a gas to the weight of…

Molecular Weight is the number which shows how many times a molecule of a substance is heavier than 1/12th part of an atom of C12 isotope. In other words molecular weight is the sum of atomic weight of all atoms present in a molecule of a substance. eg. Mol. wt. of CaCO3 =1×40 + 1×12 + 3×16 = 100 Gram Molecular Weight  When molecular weight of a substance is expressed in gram, then it is called gram molecular weight. One gram molecular weight equals to one mole and its contains 6.023×1023 molecules. For Eg. Molecular Weight of CaCO3 = 100 100gm…

STP or NTP Pressure = 760 mmHg = 1 atm T = 273K = 0°c 100ml = 1000cc = 1 LitreAt STP 1 ml or 1 cc of hydrogen = 0.000089 gm Atomic Weight = Equivalent Weight × Valency     In oxide formation method:     In Hydrogen Displacement Method:     In Chlorine Formation Method:     Q.  0.212 gram of magnesium when dissolve in hydrochloric acid and the volume of hydrogen collected over water at 16°c and 750mmHg pressure was 213.5ml. Calculate the equivalent weight of metal. Solution: Weight of metal = 0.212 gm For Hydrogen, Temperature…

According to Dulong and Petit's Law, the product of atomic weight and specific heat equals to 6.4   (Approx.). This law can be used to calculate exact atomic weight. In this method equivalent weight and specific heat are determined experimentally. Then approx. atomic weight is calculated as:- Approx. Atomic weight × Specific Heat = 6.4 Approx. Atomic Weight = 6.4/Specific Heat Again, Approx. Valency is calculated as: Approx. Valency = Approx. Atomic Weight / Exact Weight If Approx, Valency is in fraction, it is converted into whole number, which is exact valency.           Finally Exact Atomic Weight is calculated as:…