# Rice Lab Count out 1 dozen grains of rice and place in container.

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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

the mole = x 1023 602,200,000,000,000,000,000,000 Molar Mass The mass of one mole of any pure substance Episode 701

Molar mass of an element (g/mol) Molar mass of a compound
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

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

Remember Rice Lab Calculations…
How many moles of atoms are there in 8.0 grams of Mg? ? moles = 8.0g 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

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 g/mol) = g/mol 1 mol CaI2 293.9 g CaI2 6.022 x 1023 fu 1 mol CaI2 26 g CaI2 Episode 701

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 dinitrogen pentoxide? ? atoms = 3.5g Si 1mol Si x 1023 atoms = 7.5 x 1023 atoms Si 28.1g Si mol Si ? fu = 32.6 g K mol K2O x fu = 2.1 x 1023 fu K2O 94.2g K2O mol K2O ? molec = 0.25 g N2O mol N2O x molec = 1.4 x 1021 mole N2O5 108 g N2O mol N2O5 Episode 701

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