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The Mole

The Mole. The Mole. Atoms & molecules are extremely small T he number of individual particles in even a small sample of something is very large Therefore, counting the number of particles is not a practical way to measure the sample. The Mole. A chemical counting unit (abbreviated “mol”)

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The Mole

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  1. The Mole

  2. The Mole • Atoms & molecules are extremely small • The number of individual particles in even a small sample of something is very large • Therefore, counting the number of particles is not a practical way to measure the sample.

  3. The Mole • A chemical counting unit (abbreviated “mol”) • Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 • 6.02 X 1023 (in scientific notation)

  4. The Mole That’s my number! 6.02 x 1023 • This number is named in honor of Amedeo Avogadro, who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present in a constant volume of gas.

  5. The Mole • The term representative particle refers to the species present in a substance • Usually atoms or molecules

  6. Molar Relationships A balanced chemical equation can be interpreted in numbers of molecules, but generally chemists interpret equations as “mole-to-mole” relationships. 2H2(g) + O2(g) → 2H2O(l) In the equation above: 2 moles of hydrogen gas and 1 mole of oxygen gas produce 2 moles of liquid water.

  7. Molar Relationships 2H2(g) + O2(g) → 2H2O(l) Therefore: H2 & O2 have a 2:1 mole-to-mole ratio O2 & H2O have a 1:2 mole-to-mole ratio H2 & H2O have a 1:1 mole-to-mole ratio

  8. Molar Relationships N2 + 3H2 → 2NH3 What are the mole-to-mole ratios in the chemical equation above?

  9. Molar Relationships Find the number of moles of NH3 that can be formed from 4.8 mol H2 using the balanced reaction below. N2 + 3H2 → 2NH3 4.8 mol H2 2 mol NH3 3 mol H2 = 3.2 mol NH3 x

  10. Molar Relationships Find the number of moles of LiNO3 needed to produce 3.2 mol Pb(NO3)4 using the balanced reaction below. Pb(SO4)2 + 4LiNO3 Pb(NO3)4 + 2Li2SO4 3.2 mol Pb(NO3)4 4 mol LiNO3 1 mol Pb(NO3)4 = 12.8 mol LiNO3 x

  11. Practice Problems Grab your clicker! (& a calculator)

  12. Question #1 Consider the balanced chemical reaction: 2Fe + 3 H2S04 → Fe2(SO4)3 + 3H2 How many moles of Fe are required to produce 9 moles of H2? A. 9 moles B. 2 moles C. 4.5 moles D. 6 moles

  13. Question #2 Consider the balanced chemical reaction: 2Fe + 3 H2S04 → Fe2(SO4)3 + 3H2 How many moles of Fe2(SO4)3 will be produced if we begin with 17 moles of Fe? A. 17 moles B. 8.5 moles C. 34 moles D. 11 moles

  14. Question #3 Consider the balanced chemical reaction: 2C2H6 + 7O2 → 6H2O + 4CO2 How many moles of carbon dioxide are produced from 1 mole of C2H6? A. 1 moles B. 2 moles C. 7 moles D. 8 moles

  15. Question #4 Consider the balanced chemical reaction: 2C2H6 + 7O2 → 6H2O + 4CO2 How many moles of O2 are required to produce 9 moles of H2O? A. 10.5 moles B. 6 moles C. 9 moles D. 7.5 moles

  16. Question #5 Consider the following chemical reaction: KOH + H3PO4→ K3PO4 + H2O How many moles of KOH are required to produce 12.5 moles of H2O? A. 2.5 moles B. 7.5 moles C. 9 moles D. 12.5 moles

  17. Question #6 Consider the following chemical reaction: KOH + H3PO4→ K3PO4 + H2O How many moles of H3PO4 are required to produce 9 moles of H2O? A. 3 moles B. 6 moles C. 9 moles D. 7 moles

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