SG Chemistry 2A Week 4 Blog

This week in Chemistry 2A we began by learning what a moles are and the Empirical formula that prepared us for later in the week when we began our two day lab where we reacted zinc and chloride. So that we would better understand the lab we would be doing later in the week, we finished up calculations from the Relative Mass activity. This was where we had taken the masses of boxes of different types of screws and were working with these numbers, but now we connected this idea and the calculations we had came up with and applied it to chemistry and working with different elements. We discovered that each of the different nuts and bolts represented a different element, and in this case the washers represented carbon. Using the concept of relative mass, we found the ratios of the bolts and nuts to washers, and used these ratios to find out what elements the bolts and nuts represented. After multiplying each by 12.02 (atomic mass of carbon) we discovered that the bolts, with a mass of 32.9, were sulfur, and the nuts, with a mass of 16.33, were oxygen. Doing this activity where we first used objects that we were familiar with, instead of jumping right into atomic masses and elements, really helped me to visualize what we were trying to find and was a really great transition into the lab, where we began taking real life measurements.

Before jumping into the lab, we began the “Relative Mass and the Mole” worksheet where we practiced putting our newfound knowledge of the mole into context. We learned that because we can’t count every single atom in a measurement, chemists had to come up with a unit, this unit they use is called a mole. A mole is the amount of grams of an element equal to its atomic mass. An equal number of atoms is in every mole, this number is 6.02e23. I was very surprised to discover this. Dr.Finnan had us try and guess how many atoms were in a jar that he showed us, containing one mole of sulfur. I guessed way too low, only four billion. Some other students even guessed only one million! We were all very surprised.

Before we began our lab on Wednesday, Dr.Finnan made sure to demonstrate what we would be doing. Using zinc and HCL, he combined the two in a glass beaker. We noticed that it began bubbling right away and emitting a gas. I was curious as to what this gas was, and Dr.Finnan had us guessing. Someone suggested we do the flaming splint test. I predicted that the gas was hydrogen, because we know that the zinc and HCL form zinc chloride, so that means the hydrogen from the HCL must escape at some point. The flaming splint test confirmed my hypothesis.

When we did this on our own (after having took the mass of the empty beaker and the zinc) the zinc and HCL reacted the same way, fizzing and bubbling, and we were able to observe hydrogen being emitting at a closer look also, just like in the picture below.

Overnight Dr.Finnan put the beakers with the zinc and HCL on hot plates, and the next day the substance was solidified and now was called zinc chloride.

That day in the lab we had to work with bunsen burners in order to get the water out of the zinc chloride to get a more accurate measurement, and my group was a bit scared, as we had never used them before. When the beaker was being heated, it turned into a brown liquid, and gave of a strange smell.

After all the classes measurements were taken and put on the board we found that the empirical formula for zinc chloride is ZnCl2. This lab felt very empowering because we got to experiment as real chemists do in the field and work together and collaborate as a team.