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Objective:Convert between the moles and grams of a substance. Catalyst 11/3/10 Please have out homework to check. Four students conducted an experiment to test how sunlight affects plant growth. They planted 3 trays of tomatoes and measured the height of plants over a period of 25 days. Tray 1 was kept in full sunlight for the duration of each day, Tray 2 was kept in sunlight only half of the day and Tray 3 was kept in sunlight for only 3 hours each day. 1. Which of the following statements is most accurate based on the data in this chart? A. Sunlight does not affect the growth of tomato plants. B. Tomato plants will grow more slowly with decreasing amounts of sunlight. C. Tomato plants grow most rapidly when exposed to less sunlight. D. There is no correlation between growth rate and amount of sunlight. 2. Assume that one of the factors below had been used in this experiment. Which one would not have altered the outcome of the experiment? A. Fertilizer was used on Tray 3. B. Tray 1 was watered every day, while Trays 2&3 were watered every other day. C. Each Tray was given different soil. 1 D. Each student took turns tending the plants. Agenda Isotopes & atomic mass (10) Molar mass (20) Mole to mole conversions (15) Homework: Molar mass and mole to mole conversion problems 2 ISOTOPE Atoms of the same element that differ in mass. (They have the same # of p+, but different # of N°) The periodic table has masses with decimals because it gives the average atomic mass of all of the isotopes AVERAGE 11B ATOMIC MASS 10B Because of isotopes, the mass of a collection of atoms has an average value. Boron is 20% 10B and 80% 11B. That is, 11B is 80 percent of Boron on earth. For boron atomic weight = 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu Collection Terms 1 trio = 3 singers 1 six-pack Cola = 6 cans Cola drink 1 dozen donuts = 12 donuts 1 gross of pencils = 144 pencils 6 A Moles of Particles Contains 6.02 x 1023 particles 1 mole C = 6.02 x 1023 C atoms 1 mole H2O= 6.02 x 1023 H2O molecules 1 mole NaCl= 6.02 x 1023 Na+ ions and 6.02 x 1023 Cl– ions 7 Molar Mass Number of grams in 1 mole Equal to the numerical value of the atomic mass 1 mole of C atoms = 12.0 g 1 mole of Mg atoms = 24.3 g 1 mole of Cu atoms = 63.5 g 8 Learning Check Give the molar mass to 0.1 g A. 1 mole of Br atoms = ________ B. 1 mole of Sn atoms = ________ 9 Solution Give the molar mass to 0.1 g A. 1 mole of Br atoms = 79.9 g/mole B. 1 mole of Sn atoms = 118.7 g/mole 10 Molar Mass of Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole Ca x 40.1 g/mole + 2 moles Cl x 35.5 g/mole 1 mole of CaCl2 = 111.1 g/mole 2 moles N x 14.0 g/mole + 4 moles O x 16.0 g/mole 1 mole of N2O4 = 74.0 g/mole 11 Learning Check A. 1 mole of K2O = ______g B. 1 mole of antacid Al(OH)3 = ______g 12 Solution A. 1 mole of K2O = 94.2 g 2 K x 39.1 g/mole + 1 O x 16.0 g/mole B. 1 mole of antacid Al(OH)3 = 78.0 g 1 Al x 27.0 g/mole + 3 O x 16.0 g/mole + 3 x 1.0 13 Cookies and Chemistry…Huh!?!? Just like cookies have recipes, chemicals have recipes as well-we call them chemical equations Instead of using cups, we use moles Instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients Chemistry Recipes A reaction tells us how much of something you need to react with something Example: 2 Na + Cl2 2 NaCl This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride. What if we wanted 4 moles of NaCl? 10 moles? 50 moles? Mole Ratios Mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical Example: How many moles of chlorine are needed to react with 5 moles of sodium (without any sodium left over)? 2 Na + Cl2 2 NaCl 5 mol Na 1 mol Cl2 = 2.5 moles Cl2 2 mol Na Mole-Mole Conversions 2 Na + Cl2 2 NaCl How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with an excess (more than you need) of sodium metal? Practice 2 H2 + O2 2 H2O How many moles of O2 would we need if we wanted 4 moles of water? If we had 3 moles of oxygen, how much hydrogen would we need to react, and how much water would we get? What if we had 50 moles of hydrogen, how much oxygen would we need, and how much water would be produced?
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