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Chemical Compounds

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Chemical Compounds

  1. 1. ChemicalCompoundsT- 1-855-694-8886Email- info@iTutor.comBy iTutor.com
  2. 2. CHEMICAL COMPOUNDA compound, when we are talking aboutchemistry,is simply any substance that is made up of two ormore elements which react with one another.Theelements must be present in fixed ratios.-: Example :-Hydrogen and Oxygen are pure elements and aregases.© iTutor. 2000-2013. All Rights Reserved
  3. 3. CHEMICAL FORMULAA compound is represented by giving its chemicalformula, a notation that uses atomic symbolswith numerical subscripts to convey the relativeproportion of atoms of different elements in thesubstance.H2OThe two elements presenttwo H atoms per formula unitLack of subscript means one atom of O per formula unitE.g.© iTutor. 2000-2013. All Rights Reserved
  4. 4. TYPES OF CHEMICAL FORMULAEmpirical FormulaMolecular FormulaStructural Formula© iTutor. 2000-2013. All Rights Reserved
  5. 5. EMPIRICAL FORMULA The empirical formula indicates the differenttypes of elements in a molecule and the lowestwhole-number ratio of each kind of atom in themolecule. Compounds with different molecular formulascan have the same empirical formulas and suchsubstances will have the same percentagecomposition.Acetic acid (C2H4O2), formaldehyde (CH2O), andglucose(C6H12O6) all have the empirical formula CH2O.© iTutor. 2000-2013. All Rights Reserved
  6. 6. STEPS TO CALCULATE EMPIRICAL FORMULA Step 1: assume the mass to be 100g so thepercent becomes grams Step 2: determine the moles of each element Step 3: determine the mole ratio by dividingeach elements number of moles by thesmallest Step 4: Double, triple .. to get an integer isthey are not all whole numbers© iTutor. 2000-2013. All Rights Reserved
  7. 7. EXAMPLEWhat is the empirical formula given percentcomposition?62.1% of C, 5.21% of H, 12.1% of N, and 20.7% of OSolutionStep 1 : Mass is 100% so % becomes grams62.1g C, 5.21gH, 12.1g N, and 20.7g OStep 2 : determine the moles of each element62.1 g C x (12.0 g C / mole) = 5.18 moles C5.21 g H x (1.0 g H / mole) = 5.21 moles H12.1 g N x (14.0 g N / mole) = 0.864 moles N20.7 g O x (16.0 g O / mole) = 1.29 moles O© iTutor. 2000-2013. All Rights Reserved
  8. 8. EXAMPLEStep 3 : determine the mole ratio by dividing eachelements number of moles by the smallestDividing by the smallest (0.864) we getC: 5.18 / 0.864 = 6.00H: 5.21 / 0.864 = 6.03N: 0.864 / 0.864 = 1.00O: 1.29 / 0.864 = 1.49Step 4 : Double, triple .. to get an integer is they arenotall whole numbersTo get all integers, double these values and you getC12H12N2O3© iTutor. 2000-2013. All Rights Reserved
  9. 9. MOLECULAR FORMULA A molecular formula is based on an actualmolecule of a compound. It gives the exact numberof different atoms of an element in a molecule. Insome cases, the empirical formula and themolecular formula are identical E.g. formaldehyde CH2O. In other cases, themolecular formula is a multiple of the empiricalformula unit E.g. C6H12O6 = (CH2O)6© iTutor. 2000-2013. All Rights Reserved
  10. 10. STEPS TO CALCULATE MOLECULAR FORMULA Step 1 After you determine the empiricalformula, determine its mass. Step 2 Determine how many times greaterthe molecular mass is compared to the massof the empirical formula. Step 3 Multiply the empirical formula by thisnumber© iTutor. 2000-2013. All Rights Reserved
  11. 11. EXAMPLEFrom the percentages you get an empirical formula ofCH2 and the molecular mass is 56.0g/mol.SolutionStep 1 : After you determine the empirical formula,determine its mass.CH21 carbon 12.0 + 2 (hydrogens 1.0) =14.0g/molStep 2 : Determine how many times greater the molecularmass is compared to the mass of the empirical formula.molecular mass/ empirical formulas mass56.0g/mol / 14.0g/mol = 4© iTutor. 2000-2013. All Rights Reserved
  12. 12. EXAMPLEStep 3 : Multiply the empirical formula by this number4x CH2 =C4H8Note: Some compounds have the same empirical andmolecular formula.For example : Carbon Dioxide has as its empiricaland molecular formula CO2.© iTutor. 2000-2013. All Rights Reserved
  13. 13. STRUCTURAL FORMULAThe structural formula shows the elements inthecompound, the exact number of each atom inthecompound, and the bonding pattern for thecompound. The electron-dot formula and Lewisformula are examples of structural formulas.© iTutor. 2000-2013. All Rights Reserved
  14. 14. STRUCTURAL FORMULABoth compounds in the figure have two carbonatoms, six hydrogen atoms, and one oxygenatom. The difference is in the way the atomsarebonded© iTutor. 2000-2013. All Rights Reserved
  15. 15. THE ENDCall us for moreInformation:www.iTutor.com1-855-694-8886Visit

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