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Molar Quantities: Balancing Equations. CH4 + O2 = CO2 + H2O Count the atoms on each side of the equation. Reactants: 1 C ; 4 H ; 2 O Products: 1 C ; 2.

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Presentation on theme: "Molar Quantities: Balancing Equations. CH4 + O2 = CO2 + H2O Count the atoms on each side of the equation. Reactants: 1 C ; 4 H ; 2 O Products: 1 C ; 2."— Presentation transcript:

1 Molar Quantities: Balancing Equations

2 CH4 + O2 = CO2 + H2O Count the atoms on each side of the equation. Reactants: 1 C ; 4 H ; 2 O Products: 1 C ; 2 H ; (2 + 1) = 3 O

3 Reactants: 1 C ; 4 H ; 2 O Products: 1 C ; 2 H ; (2 + 1) = 3 O Double the H in the products: CH4 + O2 = CO2 + 2 H2O Reactants: 1 C ; 4 H ; 2 O Products: 1 C ; 4 H ; (2 + 2) = 4 O

4 Reactants: 1 C ; 4 H ; 2 O Products: 1 C ; 4 H ; (2 + 2) = 4 O Double the O in the reactants: CH4 + 2 O2 = CO2 + 2 H2O Reactants: 1 C ; 4 H ; 4 O Products: 1 C ; 4 H ; 4 O

5 CH4 + 2 O2 = CO2 + 2 H2O Molar coefficients for this reaction are: 1 CH4 : 2 O2 : 1 CO2 : 2 H2O

6 Molar coefficients are used for calculations. 1 CH4 + 2 O2 = 1 CO2 + 2 H2O 1 mole of methane gas (CH4) combines with 2 moles of oxygen gas (O2) to produce 1 mole of carbon dioxide (CO2) gas and 2 moles of water vapor (H2O).

7 What if we had only 0.5 moles of CH4 ??? How much CO2 would be produced ?? CH4 + 2 O2 = CO2 + 2 H2O (0. 5 moles CH4) x [ 1 mole CO2 / 1 mole CH4 ] = 0.5 moles CO2 * Note: Moles CH4 cancel out.

8 What if we had only 0.5 moles of CH4 ??? How much H20 would be produced ?? CH4 + 2 O2 = CO2 + 2 H2O (0. 5 moles CH4) x [ 2 mole H2O / 1 mole CH4 ] = 1.0 moles H2O *Note: Moles CH4 cancel out.

9 Because atoms are so small, the normal units of mass -- the gram and the kilogram -- are much too large to be convenient. One mole of something consists of 6.02 x units of that substance. One mole of carbon contains 6.02 x atoms of carbon. One mole of water contains 6.02 x molecules of water.

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11 Molar Mass (or molecular weight ) of a molecule or compound is obtained by summing the molar masses of the atoms of the compound. Molar masses of the elements are located below the element’s symbol in the Periodic Table of the Elements.

12 1 mole of CH4 molecules contains : 1 mole of carbon C atoms and 4 moles of hydrogen H atoms. Mass of 1 mol of methane: Sum of the masses C atoms and H atoms. 1 mol C = 1 x g = g 4 mol H = 4 x g = g 1 mol CH4 = g

13 What if I do not know how many moles of reactant I have ? What if, instead, I have: 200 g of CH4 = ???? moles CH4 In a mole-mass calculation, we have the added burden of converting mass to moles. For this, we need the molar masses of the reactants and/or products.

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15 What if I have: 200 g of CH4 ? How many moles of CH4 is that ? Molar mass of CH4 = 16.0 g / mol ( 200 g ) x ( 1 mol / 16.0 g ) = 12.5 mol CH4 *Note: Inversion of the molar mass

16 How many moles of CO2 will be produced by 12.5 moles of CH4 ?? CH4 + 2 O2 = CO2 + 2 H2O (12.5 moles CH4) x [ 1 mole CO2 / 1 mole CH4 ] = 12.5 moles CO2

17 How many grams in 12.5 moles of CO2 ? Molar mass of CO2: Mass of 1 mol C = 1 x 12.0 g = 12.0 g Mass of 2 mol O = 2 x 16.0 g = 32.0 g Mass of 1 mol CO2 = 44.0 g ( 12.5 mol ) x ( 44.0 g / mol ) = 550 g CO2

18 Don’t forget about the most important part of any fuel combustion reaction such as : CH4 + 2 O2 = CO2 + 2 H2O It produces heat !!

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22 If you have come here directly from the SC155 Seminar session, please return to the KU course platform now to continue with the live session of discussion, questions and answers See you all there ! 22


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