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Announcements

Announcements. To join clicker to class today: Turn on the Clicker (the red LED comes on). Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). Exam one week from today. Naming ionic compounds and acids containing polyatomic ions.

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Announcements

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  1. Announcements • To join clicker to class today: • Turn on the Clicker (the red LED comes on). • Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). • Exam one week from today. • Naming ionic compounds and acids containing polyatomic ions. • CaCl2: calcium chloride – Mn2O3: manganese (III) oxide • Na2HPO4: sodium hydrogen phosphate • H3PO4: phosphoric acid • Balancing chemical Equations • Number of each type of atom on each side must be equal. • 2H2 + O2 –––> 2H2O (4H and 2O/side) Review

  2. Mole Map

  3. Stoichiometry • Can answer questions like: How much SO3 necessary to produce the 3.959 x 1010 kg of H2SO4 manufactured in 2000? • Produced using same RXN as occurred in early atmosphere: SO3(g) + H2O(l) ---> H2SO4(aq) (balanced). • Key info • 80.064 g SO3/mol SO3 or M(SO3)= 80.064 g/mol • 98.079 g H2SO4/mol H2SO4 or M (H2SO4)= 98.079 g/mol • Route to solution (know amount of A want amount of B): mass of A -{÷M(A)}-> moles of A -{mole ratio}-> moles B -{xM(B)}-> mass B

  4. Percent Yield • All the calculations we have done so far assume that all the reactants are converted to products. Often not true: • Sometimes a limiting reagent. • Most reactions go both backwards and forwards so do not reach completion. • There are often competing RXNs that take the reactants to compounds other than the desired products. (Want: A––>B, but get some A––>D) • Poor experimental technique (losing half the sample down the drain or collecting bits of filter paper with your product). • The amount you are off by is quantified in the

  5. Example % yield • Consider elements in Earth’s crust. Compounds of Na make up about 2.5% of crust. • A common reaction of group 1 alkali metals is 2M + 2H2O –> 2MOH (metal hydroxide) + H2 • 2Na + 2H2O –> 2NaOH + H2 • Start with 23.0 g Na and an unlimited supply of H2O, what is the % yield if we got 35.0 g of NaOH • M(Na) =22.990 g Na /mol Na • M(NaOH)=39.997 g NaOH/mol NaOH

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