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Write a Balanced Equation

Write a Balanced Equation. Nitrogen gas reacting with hydrogen gas to produce ammonia You must predict the products and then balance the equation. N 2 + 3H 2 2NH 3. Chapter 12. Stoichiometry. What is Stoichiometry?.

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Write a Balanced Equation

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  1. Write a Balanced Equation Nitrogen gas reacting with hydrogen gas to produce ammonia You must predict the products and then balance the equation N2 + 3H2 2NH3

  2. Chapter 12 Stoichiometry

  3. What is Stoichiometry? • It is the calculation of the quantitative relationships in chemical equations. • A recipe for chemical equations. • Shows how mass and matter are conserved in reactions

  4. Stoichiometry- things to remember • A chemical equation must be written and it needs to be balanced. • A mole to mole conversion must exist between substances. • ALWAYS CHECK FOR DIATOMIC MOLECULES!!

  5. INTERPRETING CHEMICAL EQUATIONS 2H2 + O2 2H2O 2H2 O2 2H2O 1. # of atoms 4 2 6 2. # molecules 2 1 2 3. # moles 2 1 2 4. # grams 4 32 36 5. # Liters @ STP 2(22.4) 22.4 2(22.4)

  6. grams of substance A grams of substance B 6.02x1023 r.p. A 6.02x1023 r.p. B 1 mole of substance A 1 mole of substance B 22.4 L gas A @ STP 22.4 L gas B @ STP 2 Mole Nations

  7. Mole to Mole Ratios

  8. Mole-Mole Calculations PROBLEM: • How many moles of ammonia are produced when 0.60 moles of nitrogen reacts with hydrogen? 0.60 mol N2 ? mol NH3 (given) (unknown)

  9. STEP 1. Write a balanced chemical eq. N2 + 3H2 2NH3 STEP 2. Determine mole conversions (# moles = coefficient) 1 mol N2 1 mol N2 3 mol H2 3 mol H2 2 mol NH3 2 mol NH3

  10. STEP 3. Use dimensional analysis to solve 0.60 mol N2 2 mol NH3 1 mol N2 =1.2 mol NH3 N2 + 3H2 2NH3

  11. Mass-Mass Calculations Scientists can’t mass out moles on a balance. Therefore the amount of a substance is typically determined by measuring its mass in grams.

  12. Mass-Mass Calculations PROBLEM: • Calculate the # of grams of NH3 produced by the reaction of 5.40g of hydrogen with an excess of nitrogen. 5.40g H2 ? g NH3 (given) (unknown)

  13. Mass-Mass Calculations Step 1: Write a balanced equation N2 + 3H2 2NH3 Step 2: Know your mole conversions (#moles = coefficients) 1 mol N2 1 mol N2 3 mol H2 3 mol H2 2 mol NH3 2 mol NH3

  14. Mass-Mass Calculations N2 + 3H2 2NH3 Step 3: Use dimensional analysis to solve: Steps needed: g H2 mol H2 mol NH3 gNH3 5.40g H2 1 mol H2 2 mol NH3 17g NH3 2g H2 3 mol H2 1 mol NH3 =30.6g NH3

  15. Energy Calculations • Exothermic- a process that loses heat to the surroundings • Surrounding heat up CaO + H2O Ca(OH)2 + 65.2 kJ more PEmore KE

  16. Energy Calculations • Endothermic- a process that absorbs heat from the surroundings • Surrounding cool off 2NaHCO3 + 129 kJ Na2CO3 + H2O + CO2 more KEmore PE

  17. Energy Calculations • New conversion factor! 2NaHCO3 + 129 kJ Na2CO3 + H2O + CO2 2 moles NaHCO3 1 mole Na2CO3 129 kJ 129 kJ

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