Main Menu

(Chemistry Ch-1) 4. Laws of Chemical Combination


  • Law of Conservation of Mass:
Matter can be neither created nor destroyed.



  • Law of Definite Proportions:
A given compound always contains exactly the same proportion of elements by weight.
  • Law of Multiple Proportions:
If two elements can combine to form more than one compound, then the masses of one element that combines with a fixed mass of the other element are in the ratio of small whole numbers.



  • Gay Lussac’s Law of Gaseous Volumes:
When gases combine or are produced in a chemical reaction, they do so in a simple ratio by volume, provided all the gases are at the same temperature and pressure.



  • Avogadro Law:
Equal volumes of gases at the same temperature and pressure should contain equal number of molecules.



Dalton’s Atomic Theory
  • Postulates:
  • All matter is made of very tiny indivisible particles called atoms.
  • All the atoms of a given element are identical in mass and chemical properties whereas those of different elements have different masses and chemical properties.
  • Atoms of different elements combine in a fixed whole number ratio to form compounds.
  • Chemical reactions involve reorganisation of atoms. Atoms are neither created nor destroyed in a chemical reaction.
  • The laws of chemical combination could be explained by Dalton’s atomic theory.



Atomic and Molecular Masses
  • Atomic mass:
  • The mass of an atom
  • One atomic mass unit (1 amu) = Mass equal to one-twelfth of the mass of one carbon-12 atom
1 amu = 1.66056 × 10−24 g
  • Nowadays, ‘u’ (unified mass) has replaced ‘amu’.
  • Average atomic mass = ∑(Mass of isotope × Relative abundance)
Example
The relative abundance of two isotopes of copper, having atomic masses 62.93 u and 64.94 u, are 69.09% and 30.91% respectively. Calculate the average atomic mass of copper.
Solution:
Average atomic mass of copper = 
= 63.55 u
  • Molecular Mass:
  • Sum of the atomic masses of all the elements present in a molecule
  • Example − Molecular mass of CO2 = 1 × Atomic mass of carbon + 2 × Atomic mass of oxygen
= (1 × 12.011 u) + (2 × 16.00 u)
= 12.011 u + 32.00 u
= 44.011 u
  • Formula Mass:
  • Sum of the masses of all the atoms present in a formula unit of a compound
  • Used for compounds whose constituent particles are ions
  • Example − Formula mass of sodium chloride (NaCl)
= Atomic mass of sodium + Atomic mass of chlorine
= 23.0 u + 35.5 u
= 58.5 u
Know your scientists
Antoine Laurent Lavoisier (1743 − 1794): A French chemist and biologist postulated the “law of conservation of mass”.He is known as “the father of modern chemistry”.
Joseph Proust (1754 − 1856): A French Chemist immensely contributed to the chemical sciences by stating “the law of definite proportions”.
John Dalton (1764 − 1844): This English chemist, meteorologist and physicist is known for his pioneering work towards the development of the modern atomic theory. He postulated “the law of multiple proportions”.
Gay Lussac (1778 − 1850): A French chemist mathematically deduced volume relations and generalised his deductions as “the law of combining volumes”.
Amedeo Avogadro (1776 − 1856): An Italian scientist is known worldwide for the term “mole”. He defined the relationship between masses of same volume of different gases and their molecular weights. His law came to be known as Avogadro’s law.

10 comments:

  1. Please continue this great work and I look forward to more of your awesome blog posts. los angeles car accident lawyer

    ReplyDelete
  2. Chem Academy offering IIT JAM Online Live Classes and online video classes for IIT JAM Chemistry and Physics. We also provide IIT jam online video classes, Recorded Classes and IIT JAM online video lecture for JAM Entrance Exam. online classes for IIT jam Chemistry

    ReplyDelete
  3. Chem Academy offers CSIR NET Chemical Science coaching in Jaipur and Classroom For CSIR NET Chemical Science. According to student review and our results Chem Academy is known as Best csir net chemical science coaching in Delhi. Chemical Science Coaching for CSIR NET and CSIR NET Chemical Science Net coaching in Jaipur Available also. csir net chemical science coaching in delhi

    ReplyDelete
  4. Thermodynamics by Ved Sir | Lecture 1 | CSIR-NET | GATE | IIT-JAM | Chem Academy | Digital Board This video contains Lecture 1 of Thermodynamics which is delivered by Ved P. Sharma Sir for CSIR-NET, IIT JAM and GATE. https://www.youtube.com/watch?v=HtZJumPMgCY

    ReplyDelete
  5. It should be noted that whilst ordering papers for sale at paper writing service, you can get unkind attitude. In case you feel that the bureau is trying to cheat you, don't buy term paper from it. FUB-AMB

    ReplyDelete
  6. so happy to find good place to many here in the post, the writing is just great, thanks for the post. 4-MPD

    ReplyDelete
  7. Here at this site really the fastidious material collection so that everybody can enjoy a lot. EG-2201

    ReplyDelete
  8. I found so many interesting stuff in your blog especially its discussion. From the tons of comments on your articles, I guess I am not the only one having all the enjoyment here! keep up the good work... how to allocate more ram to minecraft

    ReplyDelete
  9. It was truly decent to peruse article composed on this blog. I might likewise want to include couple of strategies with best of my insight which can help peruser to an ever increasing extent. debt negotiation

    ReplyDelete
  10. Buy Research Chemicals online from a Trusted Supplier at best rates - interphamachem.com

    Laboratory tested High quality research chemicals for sale

    From our research chemical inventory you can:

    *buy pure AM-2201, 3-MMC,3-methylmethcathinone, mephedrone
    *4-MMC, APVP, 5F-SGT, Bis(2-ethylhexyl) Tetrabromophthalate
    *5-Methyl-dithiazinane, Ethanol, Pentetrone and much more

    Get discrete and same day delivery. Place your order today

    View the inventory of research chemicals for sale here

    ReplyDelete

Latest post

Solid State

Classification of solids: Crystalline and Amorphous solids: S.No. Crystalline Solids Amorphous solids ...