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Understanding the Mole Concept in Chemistry

Learn about the mole as a counting unit, Avogadro's constant, mole problem-solving, and mole-mass relationships in chemistry. Includes jokes and practice questions.

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Understanding the Mole Concept in Chemistry

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  1. Chapter 10 Chemical Quantities The MOLE

  2. What is a mole? A) A blind furry animal. B) A brown mark on your body. C) An important Chemistry concept. D) All of these.

  3. As you may have guessed, D is the correct answer!! Although a mole might be cute and fuzzy, we are going to focus on the Chemistry concept.

  4. A mole is a counting unit.Just like: • 12 eggs equals a dozen eggs • 144 pencils equals one gross of pencils • 60 seconds equals one minute • 500 sheets of paper equals one ream

  5. One mole equals 6.022 x 1023 particles • So one mole of eggs would be 6.022 x 1023 eggs • One mole of pencils would be 6.022 x 1023 pencils • And so on...

  6. Where did the mole come from? • The unit, called the mole (or mol), is defined as the number of atoms in exactly 12g of the carbon-12 isotope • The number of particles in one mole, 6.022 x 1023, is known as Avogadro’s constant or number. • This was named after Amedeo Avogadro (1776-1856) whose ideas were crucial to the early development in Chemistry

  7. Amadeo Avogadro

  8. 6.022 x 1023 is a very large number! • If we did not use scientific notation to write out 6.022 x 1023, we would write out 6022 with 20 zeros after it.

  9. 602,200,000,000,000,000,000,000 Wow that is a BIG number!!

  10. Imagine that we had a mole of gumballs. If all 6 billion people on Earth were to do nothing but count the gumballs in one mole at the rate of one gumball per second, it would take over 3 million years to count all the gumballs!! See pg. 316 for more

  11. What is all of this used for? • Avogadro’s constant can be used to convert an amount of moles into the equivalent number of atoms or grams.

  12. Example: How many eggs are in 8 dozen? Mole Problem Solving Strategy

  13. How many atoms are in 3.5 moles of copper? This strategy can also be used with the mole concept.

  14. convert from atoms to moles How many moles are in 3.01 x 1023 atoms of Sodium?

  15. 1. How many atoms are present in 2.25 moles CO2? 2. How many oxygen atoms are in 5.2 mol of water? 3. Find the molar mass of Cu(NO3)2 ? 4. What is the mass of 1.00 mol of Cu(NO3)2 ?

  16. If you showed all the steps, the correct answers are: 1. 4.06 x 1024 atoms • 3.1 x 1024 atoms O • 187.57 g/mol • 188 g

  17. some mole jokes! • Who is Avogadro’s favorite actor? Mol Gibson…. Ha ha! • Where did Avogadro go on Saturday? The shopping mole. • What did Avogadro have on his pancakes? Molasses!! (I know you may think these jokes are remolting, but you will grow to love them!!)

  18. One more joke Why did Avogadro look forward to the year 2000? It was the start of the new molennium!!!

  19. Sec. 10.1 Homework: Q’s pg. 309 3. How many moles is 2.80 x 1024 atoms Si? • 4. How many moles is 2.17 x 1023 representative particles Br?

  20. Q’s pg. 311 • 5. How many atoms are in 1.14 mol SO3? • 6. How many carbon atoms are in 2.12 mol C3H8? • How many H atoms are in 2.12 mol C3H8?

  21. Q’s pg. 315 • 7. Find the molar mass of PCl3? • 8. What is the mass of 1.00 mol NaHCO3?

  22. Q’s pg. 315 Lesson check 10.1 • 12. Calculate If a dozen apples has a mass of 2.0 kg and .20 bushel is 1 dz apples, how many bushels of apples are in 1.0 kg of apples? • 13. How many moles is 1.50 x 1023 molecules of NH3?

  23. Pg. 315 continued • 14. How many atoms are in 1.75 mol of CHCl3? • 15. What is the molar mass of CaSO4?

  24. Ch 10 section 2 : Mole – Mass relationships Find the number of moles in 25.6 g of Na2SO4.

  25. Calculate the mass in grams of 3.50 moles of iron(III) sulfate.

  26. Mole-Volume relationship • Avogadro’s hypothesis states that equal volumes of gases at the same temperature and pressure contain equal numbers of particles. • Note: volume of a gas varies with a change in Temp. and pressure

  27. Standard temperature and pressure (STP) means a temperature of 00C and a pressure of 1 atmosphere (atm). • For any gas: • 1 mol = 22.4 L = 6.02 x 1023

  28. What is the volume of 0.850 mol nitrogen gas?

  29. How many moles are in 55.36 L of Neon?

  30. Molar mass and density The density of a gas is 1.7824 g/L at STP. What is the molar mass of the gas?

  31. Ch 10 section 3 • Percent Composition of a compound shows the % of each element present. Ex: Fe2(SO4)3 1st add up total molar mass (P.T.) 2nd Generate each percent by using the masses of each element divided by the total mass then multiply by 100

  32. Calculate mass of element in a compound Calculate the mass of iron in 57.2 g Fe2(SO4)3. • Hint: use % comp. from previous question.

  33. Empirical Formulas Empirical Formula (simplest formula) – lowest whole number ratio of atoms in a compound. Ex/ C6H12O6 reduces to CH2O • (Basically how to go back to the formula from the percent composition)

  34. Example: Given:71.72 % Cl, 16.16% O and 12.12 % C. Calculate empirical formula. • % = grams • Convert grams to moles • Generate a ratio by dividing the mole amounts by the smallest amount of moles • Apply ratio to elements to write formula

  35. Molecular Formulas Determine the molecular formula for a compound that is 94.1% O and 5.9 % H with a molar mass of 34 g/mol. • 1st determine the empirical formula • Add up the empirical formula mass • Compare the emp. Formula mass with the given molar mass (divide the molar mass by the emp. Formula mass) then apply ratio to empirical formula

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