May 13-17

I learned more on not just how to use stoichiometry theoretically but practically as well. This week, my group and I worked on chemically combining iron and copper chloride for this lab.

The challenge was to determine how to balance the equation. Before we proceeded, of course, we massed out the nail to ensure accuracy and then we measured out the required volume of copper chloride. These steps were important to take considering the ratios of the reactants in the balanced equation. If the excess ingredient was, say the iron nail, then this means that some of it is left, which means that too much iron was used; hence, iron would be the excess ingredient. This would make copper chloride the limited reactant was enough of it was used to form the precipitate.

But, the question was what was the precipitate that would form? Initially, I guessed that it would form iron oxide because water was also used in the reaction as well. I figured because of the oxygen in water and my previous experiences with riding my bike in the puddles and leaving my brakes to rust, iron oxide would form.

Hence, the original chemical equation we came up with is:

When the reactants were reacted together, the rust on the nail came right off the nail. This supported my new hypothesis until I realized that the ions in water weren't what separated the iron and the copper chloride because when we performed the fire test (assuming that H2 gas was created, it would combust), nothing happened. Therefore, the water did not react with the iron. So, what did then?
But, my theory before that was even more ridiculous. I believed that the H2 and the Cl2 reacted together to form hydrogen chloride, but hydrogen is one of those weird elements. Even though hydrogen and oxygen are both gases, they can combine to form liquid. Since a liquid has stronger attraction between the particles than a gas, this would disprove my preposterous theory because water has a greater electronegativity than hydrogen chloride. The greater the pull on the electrons is, the greater the attraction is also.

I, was, however, considering that the iron oxidized because the red rust came off the nail, hence I still concluded that the oxygen from water didn't combine with it, but just reacted it with it. This, however, is not a plausible theory because when reactants react with each, they always form a new chemical compound or chemical compounds. Secondly, the copper chloride solution did change color, which is a sign it chemically reacted with something. Initially, the copper chloride was cyan, but when it reacted with the iron, the color changed to a greenish blue to green to greenish red.

Iron (III) Chloride and Iron (II) Chloride

I then noticed that the rust from the nail is the same color as the red solution. Since water wouldn't change the color of the solution (after all, it is colorless) nor the color of copper chloride (since it already turned cyan when it reacted to water), I concluded that it reacted with the iron. But, without the water, the chemical reaction couldn't react between iron and copper chloride because the copper chloride was powdery and the iron was metal. It doesn't make sense to combine both solids together and expect them to form new chemical compounds. The water helped to disassociate the copper chloride and turn it to a liquid so that it could transfer the electrons as it reacted with a positively charged metal. This is what happened when the copper chloride and the iron reacted together.

With this information, I changed the chemical equation and decided that iron chloride formed, and that the precipitate that formed was the copper. I noticed that to start out with, iron was neutrally charged since it wasn't chemically combined to any element and that the copper precipitate that formed was also neutrally charged. Because of this, a single replacement reaction occurred. The iron and the copper swapped places with diatomic chloride.

The stoichiometry was the last step of this lab. The amount of moles for every amount of grams had to be calculated for the reactants. First, let's consider the amount of mass the iron had before hand. Initially, it started out with 30 grams. For every 30 g, there are 0.54 moles since the atomic mass of iron is 55.85 g for every mole. The copper (II) chloride was massed at 7.5 grams. For every 7.5 g, there are 0.06 moles since the atomic mass of copper chloride is 134.45 g for every mole. Based on the ratios of the products (2 FeCl3: 3 Cu) to the reactants (2 Fe: 3CuCl2), 0.04 moles of copper (III) chloride and 0.06 moles of iron are created.