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Rice Lab

Rice Lab. Count out 1 dozen grains of rice and place in container. Repeat until you have 3 containers each holding 12 grains of rice. Mass each dozen and calculate the average mass of 1 dozen grains of rice. (Don’t forget to minus out the mass of container.)

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Rice Lab

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  1. Rice Lab • Count out 1 dozen grains of rice and place in container. • Repeat until you have 3 containers each holding 12 grains of rice. • Mass each dozen and calculate the average mass of 1 dozen grains of rice. (Don’t forget to minus out the mass of container.) • Calculate the number of rice grains in 1.94 gram of rice. • Mass out rice grains until you reach a mass equal to the mass you calculated above. • Count the grains of rice in the sample. • Calculate the percent error between the calculated number of rice grains versus the actual number of rice grains. Episode 701

  2. Mole • Avogadro’s number • the mole = 6.022 x 1023 • 602,200,000,000,000,000,000,000 • Molar Mass • Themass of one mole of any pure substance Episode 701

  3. Molar mass of an element (g/mol) • Equals the atomic mass of the element in grams • Molar mass of a compound • Equals the sum of the molar masses of the elements making up the compound • Find the molar masses of- • Magnesium g/mol • Chlorine g/mol • Magnesium chloride • Write formula • Find the atomic mass of each element • Multiply atomic mass by the number of atoms for each element, then total the masses • MgCl2 • 24.3 g/mol + (2 x 35.5 g/mol) = 24.3 35.5 95.3 g/mol Episode 701

  4. Try it! • Find the molar mass of aluminum oxide • (2x 27 g/mol) + (3 x16g/mol) • 102 g/mol Episode 701

  5. Remember Rice Lab Calculations… • How many moles of atoms are there in 8.0 grams of Mg? ? moles = 8.0g Mg • How many atoms are in 0.7 grams of He? ? atoms = 0.7g He 1 mol Mg 24.3 g/mol 1 mol He 6.022 x 1023 atoms 4.0 g/mol 1 mol He Episode 701

  6. Formula Units… No Problem • What would the mass of 5.3 x 1022 formula units of calcium iodide? Formula Molar Mass ?g CaI2 = 5.3 x1022 fu CaI2 40.1 g/mol + (2 x 126.9 g/mol) = 293.9 g/mol 1 mol CaI2 293.9 g CaI2 6.022 x 1023 fu 1 mol CaI2 26 g CaI2 Episode 701

  7. Problem Set 1 • How many atoms are in 3.5 grams of silicon? • How many formula units are in 32.6 grams of potassium oxide? • How many molecules are in 0.25 grams of dinitrogenpentoxide? ? atoms = 3.5g Si 1mol Si 6.022 x 1023 atoms = 7.5 x 1023 atoms Si 28.1g Si 1 mol Si ? fu = 32.6 g K20 1mol K2O 6.022 x 1023 fu = 2.1 x 1023 fu K2O 94.2g K2O 1 mol K2O ? molec = 0.25 g N2O5 1mol N2O5 6.022 x 1023 molec = 1.4 x 1021 mole N2O5 108 g N2O5 1 mol N2O5 Episode 701

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