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                                      Molecular Mass The mass of  molecule is referred as its molecular mass. Molecular mass is defined as the sum of the atomic masses of the atoms of all the elements present in a molecule shown by its molecular formula. For example, The molecular mass of H2o is (1 amu)*2+16 amu = 18 amu.                                          Formula Mass In many substances atoms are not organized into discrete molecules but are bonded to one another in a net work and are called Ionic Compounds. Such Compounds are represented by their simplest (Emprical) formulas e.g.NaCl, SiC etc. Formula mass is the sum of the atomic masses of atoms as given in the emprical formula of the substance. Sodium chloride is represented by the simplest formula NaCl which means that in its crystalline form, the sodium ions (Na+) and chloride ions (Cl-) occur in the ratio 1:1. Thus the formula mass of NaCl is 23 amu + 35.5 amu =58.5 amu. The formula mass of silicon carbide S

Atom is an extremely small particle. It is not possible to weigh it directly. Therefore we take its mass by comparing with slected Standard Atomic mass of C-12 (the  stable light isotope of carbon) Atomic mass is defined as the mass of one atom of the element compared with the mass of one atom of C-12. It is a number which tells how heavy or light an atom is as compared to the mass of another atom. The atomic mass of "Mg" is 24 which mean each atom of Mg is twice as heavy as Carbon atom. A Swedish chemist J. Berzelius (1779-1848) determined the atomic masses of elements. Atomic is the average of the masses of all the isotopes of an element with respect to their relative abundance. It is determined by multiplying the masses of all the isotopes which relative abundance and then add them up and finaly divide them by 100. For example:- Average Atomic Mass of Cu =63.55 a.m.u Mass spectrometer is a technique by means of which the relative abundance and atomic mass of th

Science has made great progress today. Now inventions have changed our lives completely. Man is leading a comfortable and luxurious life as a result of blessings of science. The greatest achievement of science is the fastest means of communication. People are in touch with each other around the globe with the help of phones, e-mails, faxes and satellite phones. The distances have reduced and people reach from one corner of the world to the other in supersonic jets. Harmful diseases have been eradicated with the advancement in health science. The life expectancy is increasing day by day. Food production has increased with the research in agricultural science. The ever increasing population of the world can go on eating without the fear of hunger or famine. New entertainments are available to people who can watch a large number of TV channels on cable. Mass production in modern industries is responsible for meeting needs of people. Science is providing a solution  to every pro

Cricket was the national game of England. It has now become the second national game of Pakistan too, The top six cricket teams of the world at present are Australia, India, Srilanka, New Zealand, England South Africa, Pakistan and West Indeas. The first cricket club in England was hambled which existed till 1825. This game is placed upon a large piere of levelled ground. Generally, It is played on turf. Batting is done on the pitch. On this pitch stumps are fixed 22 yards aparts. There are 3 stumps on each side. On the top of these stumps are placed two balls. There are two umpires, one at each set of stumps. There cricket match is played between two teams of eleven players each. Before the play, captains of both teams go to the umpires for toss. The winner of the toss has choice to bat or field first, Six players generally stand on the right or off side of the batsman at long off, cover point, short slip long slip and square mid-on and long-on, The man behind the wicket is cal

Allama Iqbal was born on 19th November at Sialkot, in 1877. His parents Noor Muhammad and Imam Bibi were pious and religious persons. He passed his matriculation and intermediate exams in 1893 and 1895 respectively. He did his B.A from Government College, Lahore in 1897 and M.A in philosophy in 1899. He took his Doctorate Degree from Munich (Germany). His thesis was "Philosophy Of Ajam". After talking his Barrister's Degree from London, In 1908; he returned home. After returning from England he started practice as a Barrister in 1908. The poet was born in him from early age. He wrote poetry under inspiration. He had written poetry in Urdu and Persian. Allama Iqbal has left valuable and voluminous treasures of Poetry and Prose after him. The following are famous poetic works of Iqbal: Israr Khudi (1915), Ramuz-e-Bekhudi (1918) Paigham-e-Mashriq (1923), Javed Nama (1932) and Musafir (1934) are his great works in Persian. Bange-e-Dira (1924) Bal-e-Jibrael (1935) and Zarb-

What are Significant Figures? The reliable digits in a number that are known with the certainty are called significant figures. The last digit of measured number is generally considered uncertain by ± 1. For Example :  0.0112g contains three S.F and uncertainty is ± 0.0001 mg. 11/2mg contains three S.F and uncetainty is ± 0.1mg. The uncertainty and the number of S.F do not change when measurement is expressed in sub units. For Example: 0.0112g = 11.2mg in 0.0112g uncertainty is ± 0.0001g and in 11.2 mg uncertainty is ± 0.1mg as 0.0001g = 0.1mg. Therefore uncertainty and number of S.F do not change. Number Of Significant Figures (Digits) Depends Upon : The accurancy of the measuring instrument. The size of the object to be measured. In any series of measurements, the measured numbers are obtained to a certain degree of precision. The precision of measured is indicated by the number of significant figures. Precision : How close a series of measureme