General Types of Reactions Notes

# Simplest ration of all moles by dividing all moles by

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Simplest ration of all moles by dividing all moles by smallest mole 4. IF one (or more) of atoms in a fraction multiply all atoms by coe ffi cient to obtain whole numbers Empirical formula 5. Sum of atoms in empirical formula (Empirical weight) 6. Estimated molecular weight/ empirical weight to fine coe ffi cient (whole number) 7. Use that whole number multiply all subscripts in empirical formula by coe ffi cient to obtain Molecular Formula. "percent to mass, mass to mole, divide by small, multiply by whole" Mass % elements

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Empirical formula Grams of Each element Moles of each element From our combustion reaction, we obtained that a compound has 40.92 % C, 5.58% of H, and 54.50 % O. From mass spectrometer, the formula weight is approx. 176 amu, What is empirical and molecular formulas? 1. 100g sample x (40.92g C/ 100g sample) = 40.92 g C 100g sample x (4.58g H/ 100g sample) = 4.58 g H 100g sample x (54.50g O/ 100g sample) = 54.50 g O 2. 40.92g C x (1 mol C/ 12.01) = 3.407 mol C 4.58g H x (1 mol C/ 12.01) = 4.544 mol H 54.50g O x (1 mol C/ 12.01) = 3.406 mol O <---- smallest mol 3. (3.407/3.406) = 1.00 (4.544/3.406)=1.33 (3.406/3.406)=1.00 4. Multiple by 3 ---> C 3 H 4 O 3 (right) instead of C 1 H 1.33 O 1 (WRONG) 5. Emp. Weight= 3(12.01) + 4(1.008) + 2(16.00) = 88.1 amu (remember that FW is 176 amu) 6. To find coe ff to multiply Emp. Formula 7. 176 amu/88.1 amu= 2 (should be a whole number) 8. C 3 H 4 O 3 x 2 = C 6 H 8 O 6 (answer) this is the Molecular Formula!!
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