Day 2.25 Turning Mass to Moles for the 1st Time!

Wed. Mar 5, 2014

2014-03-05 10.39.56 2014-03-05 10.40.25

 

Late last week chemistry 1 students reacted zinc metal with hydrochloric acid.  After another long weekend we dried and massed the product, zinc chloride yesterday.  Today groups analyzed their data by figuring out how much zinc was reacted, zinc chloride was produced, and chlorine was in the product.

The challenge then came in as to how to analyze the ratio of atoms being used in the reaction, and not the masses.  Through some discussion students realized they could use the unit of moles to “count” the atoms.  But how?  I came back to the idea of relative masses and the masses listed on the periodic table.  We decided that if 1 atom of Zn has a mass of 65.38 amu and 1 atom of Cl has a mass of 35.45, why couldn’t 1 MOLE of Zn have a mass of 65.38 GRAMS, and 1 MOLE of Cl have a mass of 35.45 GRAMS!  As long as we are comparing equal numbers of particles the mass ratios should be the same!

This is where we left off today, and tomorrow we will be able to analyze the mole ratio for the Zn and Cl and be able to write an empirical formula for the Zinc Chloride compound.

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About bradwysocki

I teach high school Chemistry and Physics using Arizona State University's Modeling Method. The school I teach in is Bloomer HS in Northwest Wisconsin. I've been using the Modeling Method for 7 years now and have just recently begun using Standards Based Grading as a way to assess my students learning.
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