Chapter 2 Atoms and the atomic theory.pptx - Chapter 2:...

This preview shows page 1 - 9 out of 56 pages.

Chapter 2:Atoms and theAtomic Theory
2-1 Early Chemical Discoveriesand the Atomic TheoryChemistry has been practiced for a very long timeThe blast furnace for extracting iron from ironore,and such important chemicals assulfuric acid,nitric acid, andsodium sulfatewere all wellknown and used several hundred years ago.Yet chemistry can’t be said to have entered themodern age until the process ofcombustionwasexplained.
Law of Conservation of MassIn 1774, Antoine Lavoisierperformed an experiment in which he heated a sealed (closed) glassvessel containing a sample of tin (Sn) and some air.He found that themassbeforeheating and afterheating were thesame.Law of conservation of mass:The total mass of substances presentafter a chemical reaction is the same as the total mass of substancesbefore the reaction.
Mass is conserved during achemical reaction(a) Before the reaction, a beakerwith a silver nitratesolution and agraduated cylinder with apotassium chromatesolution(b) When the solutions are mixed, achemical reaction occurs thatforms silver chromate (redprecipitate)Note that the total mass 104.50 gremains unchanged.
EXAMPLE 2-1 Applying the Law of Conservation of MassA0.455 g sample of magnesiumis allowed to burn in2.315 g of oxygengas. The sole product is magnesium oxide.After the reaction, nomagnesium remains and the mass of unreacted oxygen is 2.015 g. Whatmass of magnesium oxide is produced?
The total mass is unchanged.The total mass is the sum of the masses of the substances presentinitially.The mass of magnesium oxide is the total mass minus the mass ofunreacted oxygen.
PRACTICE EXAMPLE A:A0.382 g sample of magnesiumis allowed to react with2.652 g ofnitrogen gas.The sole product ismagnesium nitride. After the reaction,the mass ofunreacted nitrogen is 2.505 g. What mass of magnesiumnitride is produced?

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 56 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Summer
Professor
N/A
Tags

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture