Formula Units Determination for Magnesium Chloride

This video summarizes an experiment performed to experimentally determine the formula ulnits of magnesium chloride.

In the lab the mass of a small sample of magnesium ribbon is measured. The metal is then placed into a beaker and concentrated HCl is added. When the reaction is complete the beaker is heated to drive off water and any unreacted HCl. Safety Note: This should be done in a fume hood to avoid breathing in any HCl fumes!

 After all the liquid has been removed from the beaker a precipitate of magnesium chloride is left behind.
The mass of this compound is measured and compared to the original amount of magnesium to determine the added mass of chlorine. The data collected allows students to calculate the formula units of the magnesium chloride salt.



The reaction is summarized by the following chemical equation.

2Mg  +  HCl → MgCl2 + H2

The compound forms with a 1:2 ratio of magnesium to chlorine. This is because magnesium has two valence electrons which are donated to the chlorine atoms. The chlorine atoms have seven valence electrons which allow them to add one valence electron during the formation of a chemical bond.

I hope this was helpful.

Comments

Post a Comment

Popular posts from this blog

Radioactive Dinner Plate

Image
This video shows two plates being measured for emission of radiation. The orange Fiesta plate was made using a glaze which contains uranium oxide. Fiesta dinnerware was produced by the Homer Laughlin China Company of West Virginia. Prior to World War II the glazes used natural uranium.  This practice stopped during the war when the US government seized the company's stock of uranium for the Manhattan Project.  In the late 1950's the Atomic Energy Commission relaxed restrictions on uranium and production practices switched to using depleted uranium to produce the red-orange glaze. The US Environmental Protection Agency recommends that dinnerware produced with uranium glaze should not be used for food, drink or food storage.
Read more

The Effect of Concentration on the Rate of a Chemical Reaction

Image
This video shows a classic lab examining the effect of concentration of reactants on the rate of a chemical reaction.  This video supports NGSS HS-PS1-5 . In this experiment solutions of sodium thiosulfate and hydrochloric acid are combined in a beaker.  The reaction produces a precipitate which eventually makes the liquid turn cloudy.  The reaction beaker is placed over a piece of paper with a letter "X" printed on it.  The reaction is said to have gone to completion when the "X" can no longer be seen through the liquid in the beaker. I have used this video as a warm up or as a flipped lesson which has students make observations, record data about the reaction time for the trials, create a graph and form a conclusion about the effect concentration has on the speed of a chemical reaction. This lab was originally published by Flinn Scientific as a Chem Fax!  Use this link to see the full description of the experiment.
Read more