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Ratios Used in Chemistry

Ratios Used in Chemistry. Find a Method that Works for You. The Kill Method. Start by drawing the “target frame” In the top left corner, put in the information given from the QUESTION In lower right corner, put in the MOLAR RATIO that cancels out the units found in step 2

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Ratios Used in Chemistry

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  1. Ratios Used in Chemistry Find a Method that Works for You

  2. The Kill Method • Start by drawing the “target frame” • In the top left corner, put in the information given from the QUESTION • In lower right corner, put in the MOLAR RATIO that cancels out the units found in step 2 • In upper right corner, put in the MOLAR RATIO that is found in the equation of WHAT YOU ARE LOOKING FOR • Multiply across the top, then divide across the bottom

  3. The Kill Method 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? 1. Start by drawing the “target frame”

  4. The Kill Method 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? 2. In the top left corner, put in the information given from the QUESTION 578 moles of CH4

  5. The Kill Method 4 CH4+ 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? 3. In lower right corner, put in the MOLAR RATIO that cancels out the units found in space 1 578 moles of CH4 4 moles of CH4

  6. The Kill Method 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? 4. In upper right corner, put in the MOLAR RATIO that is found in the equation of WHAT YOU ARE LOOKING FOR 578 moles of CH4 6 moles of H20 4 moles of CH4

  7. The Kill Method 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? 5. Multiply across the top, then divide across the bottom 578 moles of CH4 6 moles of H20 = 3468 = 867 4 mols H20 4 moles of CH4

  8. Cross Multiply • ONLY WORKS FOR RATIOS! • MUST BE ALIGNED PROPERLY Both are CH4 4 mols CH4 = 578 mols CH4 6 mols H2O 867 mols H2O Both are H20 Both are from the QUESTION Both are from the EQUATION

  9. Cross Multiply 4 CH4+ 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? • Start with the ratios found in the EQUATION (Note: they can be in any order – either top or bottom provided that you follow the alignment) 4 mols CH4 6 mols H2O

  10. Cross Multiply 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? 2. Next, make an equivalent equation using the information from the QUESTION – Make sure that it lines up appropriately 4 mols CH4 = 6 mols H2O 578 mols CH4 ? mols H2O

  11. Cross Multiply Review of how to align the expression 4 mols CH4 = 578 mols CH4 6 mols H2O 867 mols H2O Both are CH4 Both are H20 Both are from the QUESTION Both are from the EQUATION

  12. Cross Multiply 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? • MULTIPLY ACROSS 4 mols CH4 = 578 mols CH4 6 mols H2O ? mols H2O 578 mols CH4 x 6 mols H2O = 3468 mols CH4 x H2O Note: This can be “crossed” either way or

  13. Cross Multiply 4 CH4 + 7 O2 → 4 CO2 + 6 H2O • We start the reaction with 578 moles of CH4 (methane). How many moles of water will be produced? • DIVIDE BY THE OTHER AMOUNT 4 mols CH4= 578 mols CH4 6 mols H2O ? mols H2O 3468 mols CH4 x H2O / 4 mols CH4 = 867 mols H2O

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