Rice Lab 1 Count out 1 dozen grains

Rice Lab 1. Count out 1 dozen grains of rice and place in container. 2. Repeat until you have 3 containers each holding 12 grains of rice. 3. Mass each dozen and calculate the average mass of 1 dozen grains of rice. (Don’t forget to minus out the mass of container. ) 4. Calculate the number of rice grains in 1. 94 gram of rice. 5. Mass out rice grains until you reach a mass equal to the mass you calculated above. 6. Count the grains of rice in the sample. 7. Calculate the percent error between the calculated number of rice grains versus the actual number of rice grains. Episode 701

Mole • Avogadro’s number – the mole = 6. 022 x 1023 – 602, 200, 000, 000 Molar Mass The mass of one mole of any pure substance Episode 701

• 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 24. 3 g/mol – Chlorine 35. 5 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 • Mg. Cl 2 • 24. 3 g/mol + (2 x 35. 5 g/mol) = 95. 3 g/mol Episode 701

Try it! • Find the molar mass of aluminum oxide (2 x 27 g/mol) + (3 x 16 g/mol) 102 g/mol Episode 701

Remember Rice Lab Calculations… • How many moles of atoms are there in 8. 0 grams of Mg? ? moles = 8. 0 g Mg 1 mol Mg 24. 3 g/mol • How many atoms are in 0. 7 grams of He? ? atoms = 0. 7 g He 1 mol He 6. 022 x 1023 atoms 4. 0 g/mol 1 mol He Episode 701

Formula Units… No Problem • What would the mass of 5. 3 x 1022 formula units of calcium iodide? Ca. I 2 Formula Molar Mass 40. 1 g/mol + (2 x 126. 9 g/mol) 293. 9 g/mol ? g Ca. I 2 = 5. 3 x 1022 fu 1 mol Ca. I 2 6. 022 x 1023 fu = 293. 9 g Ca. I 2 1 mol Ca. I 2 26 g Ca. I 2 Episode 701

Problem Set 1 • How many atoms are in 3. 5 grams of silicon? ? atoms = 3. 5 g Si 1 mol Si 28. 1 g Si 6. 022 x 1023 atoms = 7. 5 x 1023 atoms Si 1 mol Si • How many formula units are in 32. 6 grams of potassium oxide? ? fu = 32. 6 g K 20 1 mol K 2 O 6. 022 x 1023 fu 94. 2 g K 2 O 1 mol K 2 O = 2. 1 x 1023 fu K 2 O • How many molecules are in 0. 25 grams of dinitrogen pentoxide? ? molec = 0. 25 g N 2 O 5 1 mol N 2 O 5 6. 022 x 1023 molec 108 g N 2 O 5 1 mol N 2 O 5 = 1. 4 x 1021 mole N 2 O 5 Episode 701