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Solving Equations Algebraically

Solving Equations Algebraically. When propyl alcohol, CH 3 CH 2 CH 2 OH, burns in air, it reacts with oxygen, O 2 , to form carbon dioxide, CO 2 , and water, H 2 O. Write the balanced chemical reaction. Take out a piece of paper and a pencil and go through this example with me.

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Solving Equations Algebraically

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  1. Solving Equations Algebraically

  2. When propyl alcohol, CH3CH2CH2OH, burns in air, it reacts with oxygen, O2, to form carbon dioxide, CO2, and water, H2O. Write the balanced chemical reaction.

  3. Take out a piece of paper and a pencil and go through this example with me. • We will use algebra to solve for the coefficients. • It's a 6-step process

  4. Step 1 Identify the reactants and products • Reactants propyl alcohol, CH3CH2CH2OH oxygen, O2 • Products carbon dioxide, CO2 water, H2O

  5. Step 2 Write the unbalanced chemical equation CH3CH2CH2OH (l) + O2 (g) --> CO2 (g) + H2O (l)

  6. Step 3 Assign variables as coefficients for each substance in the chemical equation. "a" for the coefficient of CH3CH2CH2OH "b" for the coefficeient of O2 "c" for the coefficeient of CO2 "d" for the coefficeient of H2O a CH3CH2CH2OH (l) + b O2 (g) --> c CO2 (g) + d H2O (l)

  7. Step 4 Determine the number of each type of atoms on each side of the arrow. a CH3CH2CH2OH (l) + b O2 (g) -->cCO2 (g) + d H2O (l) 3a+ 0 = c + 0 8 a + 0 = 0 + 2 d a+ 2 b = 2 c + d Carbon Hydrogen oxygen

  8. Step 5 Write out the algebraic equations and solve for the coefficients. a CH3CH2CH2OH (l) + b O2 (g) --> c CO2 (g) + d H2O (l) equation (1) 3a = c equation (2) 8a = 2 d equation (3)a + 2 b= 2 c + d

  9. Let a = 1, and solve: equation (1) becomes 3 = c equation (2) becomes 8 = 2 d, OR 4 =d equation (3) becomes 1 + 2 b = 6 + 4, OR b = 9/2 Substitute back into the chemical equation, we get CH3CH2CH2OH (l) + 9/2 O2 (g) --> 3 CO2 (g) + 4H2O (l)

  10. Step 6 Make sure that all the coefficients are whole numbers. Multiply all the coefficients by an appropriate factor to convert any fractions to whole numbers. Remove the fractions by multiplying through by 2: 2 x ( CH3CH2CH2OH (l) + 9/2 O2 (g) --> 3 CO2 (g) + 4H2O (l) ) The balanced equation is: 2 CH3CH2CH2OH (l) + 9O2 (g) 6CO2 (g) + 8H2O (l)

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