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Warmup (5 minutes)

Warmup (5 minutes) A “dozen” is what we call a “counting unit.” What are some other counting units? Write the formula for aluminum sulfate Do atoms ever disappear from our universe?. Equations. and the Mole.

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Warmup (5 minutes)

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  1. Warmup (5 minutes) • A “dozen” is what we call a “counting unit.” What are some other counting units? • Write the formula for aluminum sulfate • Do atoms ever disappear from our universe?

  2. Equations and the Mole You will have another Memorization Quiz next class: ions again, and solubility rules too!

  3. In science, a mole is how we count the number of a substance (like a dozen).

  4. How much is a mole? The number of things in 1 mole has been determined to be: 6.02 x 1023 This is Avogadro’s Number (after the scientist who figured it out). 602000000000000000000000 is the number of atoms in 12 grams of carbon.

  5. Is one mole always the same quantity? Yes: for # molecules or atoms No: for mass 1 mole silicon atoms 1 mole iodine atoms 6.02x1023 atoms in each box Mass = 28.09 grams Mass = 126.90 grams

  6. 2 moles1 mole (no #) 2Na(s)  +  2H2O(l)  →  2NaOH(aq)  +  H2(g) solid liquid aqueous gas Reactants Products arrow = “yield”, “make”, “produce”, “form” Translate the equation into a sentence! 2 moles of solid sodium react with 2 moles of liquid water to yield 2 moles of aqueous sodium hydroxide and 1 mole of hydrogen gas(Why H2?)

  7. Diatomic Elements are: gaseous elements which are unstable if found as a single atom; H2 O2 F2 Br2 I2 N2 Cl2 Write an equation: 2 moles of solid sodium react with 1 mole of chlorine gas to yield 2 moles of aqueous sodium chloride 2Na(s) + Cl2(g)  2NaCl(aq)

  8. Write the equation: solid calcium reacts with aqueous hydrogen chloride to yield aqueous calcium chloride and hydrogen gas Ca(s)  +   HCl(aq)  →   CaCl2(aq)  +   H2(g) Is this equation balanced? 1 1 2 1 Law of conservation of matter: in a chemical reaction, matter is neither created nor destroyed

  9. A balanced equation obeys this law; it has equal numbers of each type element on both sides of the equation. “what goes in, comes out!” 2 1 2 _____H2 + _____ O2 _____ H2O

  10. Balancing Tips 1) Use a pencil, you might have to erase! 2) It helps to balance metal atoms first, H’s and O’s last! 3) Place whole-number coefficientsin front of the formulas; NEVER change subscripts in the chemical formula. “1” is not completely necessary. 4) Multiply new coefficient times the subscript to count the total # atoms for that element on each side. (Example: 2H2= 4 hydrogen atoms total) It takes practice…you will not learn by watching!

  11. __Al (s) + __Fe2O3(aq) → __Al2O3(aq)+ __Fe(s) Balancing Example: #1 2 1 1 2 Al Fe Fe O O O Al Al O O O Fe Al Fe

  12. 2 minutes! 3 1 2 2 __C2H4 + __O2→ __CO2 + __H2O 3 ____ N2 + ____ H2 ____ NH3 1 2

  13. Be Careful With Parentheses: • How many atoms are in: 3Mg(OH)2 Mg(OH)2 3Mg(OH2)2 1 3 3 # of Mg atoms: # of Oatoms: 2 6 6 6 12 # of Hatoms: 2

  14. A hamburger is made of certain materials: • Bun • Lettuce • Meat • Bun • What would an equation for the synthesis of one hamburger look like? 2 1 1 1 ____Bun + ____Lettuce + ____Meat  ____hamburger

  15. Mole Ratio Problems • If I wanted to make 20.5 hamburgers, how many buns would I need? 20.5 hamburger (2 buns) = 41.0 buns (1 hamburger) • How many hamburgers can I make if I had 17 meats (assuming I have enough of everything else)? 2 17 meats 1 (1 hamburger) 1 1 ____Bun + ____Lettuce + ____Meat  ____hamburger = 17 hamburgers (1 meat)

  16. 1N2 + 3H22NH3 Translate the equation above into a sentence: If 1 moleN2 reacts with 3 moles H2, 2 moles NH3 are produced. Write all the molar ratios possible given this equation The molar ratio compares the number of moles of each compound in an equation. I will sometimes say ‘molecules’ to simplify, although this is technically inaccurate. 1 mole N23 moles H21 mole N2 3 moles H2 1 mole N2 2 moles NH3 2 moles NH33 moles H22 mole NH3 1 mole N2 2 moles NH33 moles H2

  17. If2 moles of N2are used, how many moles of NH3will be produced in the reaction? 1N2 + 3H22NH3 2moles N2 (2moles NH3)= 4 moles NH3 (1mole N2) If you want 7.70 moles of NH3, how muchH2is needed? 7.70 moles of NH3 (3 moles H2) = (2 moles NH3) 11.6 moles H2 Warning: Sometimes you will have to balance the equation first!

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