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Stoichiometry

Stoichiometry. Stoichiometry Steps. Balance the equation;. Is it balanced?. Is it balanced?. Mole Box. Grams A. Grams B. Molar Mass of A. Molar Mass of B. Mol A. Mol B. Mole Ratio (Balanced Equation). 2. Grams to Moles (Divide by Molar Mass) *Don’t forget to use sig figs!*.

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Stoichiometry

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  1. Stoichiometry

  2. Stoichiometry Steps • Balance the equation; Is it balanced? Is it balanced?

  3. Mole Box Grams A Grams B Molar Mass of A Molar Mass of B Mol A Mol B Mole Ratio (Balanced Equation)

  4. 2. Grams to Moles (Divide by Molar Mass)*Don’t forget to use sig figs!* A samplecontains 27.1 g of oxygen. How many moles of oxygen are in thissample? 27.1 grams of O2 X 1 mole O2 = 32 grams O2 0.847 moles of O2 This is the molar mass of Oxygen. (16.00g X 2)= 32.00g of O2 *THIS IS A ONE STEP PROBLEM!*

  5. 3. Moles to Moles ( Multiply by Mole Ratio) If you started with 3.50 mol of hydrogen, how many moles of oxygen could be formed? 3.50 mol H2 X 1 mole O2 = 1.75 moles of O2 2 moles H2

  6. 4. Mole to Grams (Multiply by Molar Mass) If you needed to produce 12.2 g of water, how many grams of hydrogen would you need? 12.2 moles of H2O X 2 moles H2 X 2 grams H2 = 24.4 grams of H2 2 moles H2O 1 mole H2 *THIS IS A TWO STEP PROBLEM!*

  7. Molarity The concentration of a solution in mol/L = moles of solute 1 L of solution

  8. Finding Moles of a Solution Use the formula; cv = n Concentration(mol/L) X Volume(L) = Moles(mol)

  9. Mole Box 2 Grams B Grams A Molar Mass of A Molar Mass of B Mol B Mol A Mole Ratio (Balanced Equation) Concentration of A (mol/L) Concentration of B (mol/L) Litres A Litres B

  10. Example(Litres A to Grams B) 2 NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l) 15.0 mL of a 1.5 mol/L NaOH solution gives how many grams of H2O? 0.0150 L NaOH X 1.5 mol NaOH X 2 mol H2O X 18g H2O = 1 L NaOH 2 mol NaOH 1 mol H2O CONVERT! 1 L = X L X= 0.0150 L 1000 mL 15.0 mL 0.405 g H2O *THIS IS A THREE STEP PROBLEM!*

  11. Stoichiometry with Gases The stoichiometry of gases is based on the ratio between the quantities of gas involved in a chemical reaction. This method is used to predict the quantity of a reactant or productinvolved in a chemical reaction in which one of the compounds is a gas.

  12. Example 1(Litres A to Litres B) If 7.00 L of H2 gas reacts with Cl2 gas, how many litres of HCl gas would form? H2 + Cl2 2HCl 7.00 L H2 X 2 L HCl = 14.0 L HCl 1 L H2

  13. Example 2(Grams A to Litres B) Mg(s) + HCl(aq) MgCl2(aq) + H2(g) • If 17.00 g of Mg reacts, how many millilitres of H2 will form? 17.00 g Mg X 1 mol Mg X 1 mol H2 X 22.4 L H2 = 15.70 L of H2 24.31 g Mg 1 mol Mg 1 mol H2 1 L = 15.70 L X= 15 700 mL of H2 1000 mL X mL Convert this answer to millilitres!

  14. Classifying Reactions • Combustion= Burning with Oxygen Tips: • If C is in the reactants, CO2 will be a product. Example: • C + O2 CO2 • If H2 is in the reactants, H2O will be a product. Example: • 2H2 + O2 2H2O • CH4 + 2O2 CO2 + 2H2O

  15. 2. Synthesis Simpler reactants combine to make more complex products. Examples: • Mg + Cl2 MgCl2 • CO2 + H2O H2CO3

  16. 3. Decomposition Decomposition is when complex Reactants break down to become simpler molecules. Examples: • H2CO3 H2O + CO2 • BF3NH3 BF3 + NH3

  17. 4. Single Displacement An element and a compound are required for single displacement. The element in the reactants will “replace” or “displace” one of the elements in the compound. *It is important to remember that metals replace metals only, and non-metals replace non-metals only. Examples: • A + B B + AC • Na(s) + H2O(l) NaOH(aq) + H2(g)

  18. Example of a Reaction Burning of methane releases 275 kJ of energy per mole of methane being burned. How many grams of methane must burn in order to produce 1500 kJ of energy? CH4 + 2O2 CO2 + 2H2O 1500 kJ X 1 mole CH4 X 16.04 g CH4 275 kJ 1 mole CH4 What type of reaction has occurred? Combustion reaction. = 88 g of CH4 C = 12.01 12.01 + 1.01(4) = 16.04 g of CH4 H = 1.01

  19. Bibliography • Couture, Ivan, Marie-Eve Lacombe-Harvey, and Genevieve Levasseur-Thériault. Quantum Chemistry Student Textbook. Ed. Marie-Eve Robitaille, Isabel Rusin, and Colleen Ovenden. Trans. Jacquie Charlton, Cristina Cusano, Natasha DeCruz, Joann Egar, and Gwen Schulman. Montreal: Cheneliere Education, 2011. Print. • Doty, Wendy L. "Stoichiometry Notes." Downey Unified School District. N.p., 2006. Web. 10 Oct. 2012. <http://www.dusd.net/staff/rcramm/Chemistry/Unit_8/Stoichiometery%20Notes.pdf>.

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