Blog #4

This past week, our main focus of learning had to do with relative mass and moles. We started off with a worksheet that had different tables where we needed to figure out the masses of different samples. The first table gave us different numbers of chicken/quail eggs, and we needed to figure out their masses.We were given the mass of one egg, so we used that knowledge to see how massive up to a million eggs were. The ration between the masses of both types of eggs were 16:1, for every amount of eggs given. This showed that chicken eggs are 16 times heavier than quail eggs. In the next example we looked at how many atoms were in different samples. For oxygen, when there was a one atom sample, the mass was 16.00 amu. But, when there was one mole in the sample, there were 16.00 grams. We saw that a mole contained the same mass as a one atom sample, just with different units. This introduced us to the mole which we then learned by Avogadro’s theorem is 6.022 * 10^23 particles.

Above is a picture of the third model we looked at comparing different elements masses when there is one atom, vs. when there is one mole. This reinforced that one atom has the same number as one mole, just atoms are measured in amu, while moles are measured in grams.

After this worksheet we did the Empirical Formula Lab. In this lab we took zinc and reacted it with hydrochloric acid to produce zinc chloride, and then figured out the empirical formula (formula based on experimental evidence). My group found the mass of the beaker itself to be 31.89g, and then found the mass of the beaker with zinc to be 34.98g. After getting these masses, we placed the beaker on a hot plate until we the next day. The next day we used a bunsen burner to heat the beaker to get the substance bubbling, and then stopped heating it as soon as the content began to smoke. We then let it cool, and noticed how the zinc chloride started to solidify. After this, we found the mass to be 38.155g, and repeated the heating step again to find the mass to be the same the second time. We looked at the class data, and compared the mass we found the zinc and Cl mass to, and also compared their moles. Every table group had different answers, but they were all very close to each other. In the end, each table came to the same empirical formula which was ZnCl2. Below is a picture of the class data.

After briefly touching upon finding the mass and mole of an atoms in worksheets and the empirical experiment, we started to practice more problems that had to do with finding how many atoms and moles are in certain substances. For example we were asked to find how many moles of iron atoms were in 4.42 grams of iron. To figure this out, you take the mass of the substance you are testing which in this case is 4.42g, and multiply it by 1 mol of iron divided by the mass of the element iron itself which is 55.845g. Then you get your answer to be .079 mol of iron. After doing many problems like these in class and for homework, I came to a good understanding of what the mol really is, and how to calculate it. Everything we did this week really tied to the mol of elements, and how they differ for different substances.