# Can one determine the coefficients of a balanced chemical equation by having the mass of a reagent, the mass of the dry product and by using stoichiometry?

Purpose

Can one determine the coefficients of a balanced chemical equation by having the mass of a reagent, the mass of the dry product and by using stoichiometry?

Hypothesis

If the mass of the aluminum and the mass of the dry product, copper, is known then the balanced chemical equation can be derived by converting the masses to moles by dividing by the empirical molar masses of the elements, and then one can do a mole to mole ratio between this product and the reactant to make a balanced chemical equation. In a balanced chemical equation the coefficients of the chemical equation are indicative of the ratio of  moles of the reactants and the products in a reaction. Since molar mass is also the mass per mole of substance and one knows the mass, then if one divides the mass determined from the experiment by the molar masses of each element then logically one will get the number of moles of the substance. From there a mole to mole ratio can be done between the product and the reactant and since a chemical equation can not have a fraction as a coefficient, then the coefficients can be multiplied on both sides by a number that will get a whole number for both elements. Since the law of conservation of mass states that anything that any quantity of substance that is put into the equation must result in the same quantity coming out of it and vice versa. This means that the very same mole to mole ratio can be applied to copper(ii) chloride and aluminum chloride to get the coefficients on those compounds.  Hence finding the balanced chemical equation of the reaction.

Procedure

1. Before the experiment is performed, two data tables are constructed. This is crucial because the time in the lab must be used efficiently, and time cannot be wasted in creating data tables which must be used for recording qualitative and quantitative observations. Data tables should resemble the ones outlined below.

1. Take a 2.50g strip of aluminum and make sure that it is shined so that any oxidized aluminum is removed. Any oxidized aluminum could interfere with the precision as well as the accuracy of the mass of the aluminum. In addition the oxidized aluminum would not react with the copper(ii) chloride to get a desired outcome, since the product of aluminum oxide and copper(ii) chloride solution is copper(ii) oxide which is solid. This would alter the mass of the copper at the end of the experiment, endangering the precision of the experiment.
2. Calibrate the OHAUS Precision Standard balance to 0.00g to upkeep the precision of the experiment.
3. Determine the mass of the strip of aluminum so that the data for the moles of aluminum can be determined at a later point in the lab. This is because molar mass is a empirical number that can be determined from aluminum and since moles is the undetermined variable, mass needs to be determined. Record this data in “Data Table 2 – Quantitative Data Table” under “Mass of Aluminum(±0.01g)”.
4. The properties of the strip of aluminum is also determined so that it can be ensured that the aluminum is not oxidized and that the properties of the aluminum fits the properties of what aluminum is actually supposed to look like. Record this in “Data Table 1 – Qualitative Data Table” and record it under “Before Reaction”.
5. Take 7.50g of copper(ii) chloride salt and spray it with water in a 150mL beaker until the whole salt is dissolved in an aqueous solution. Solid copper(ii) chloride will not react with aluminum because the intermolecular forces of the compound are too strong to be able to undergo the displacement that the reaction entails. This is why the copper(ii) chloride needs to be in a solution. Ensure that the solution is in a 150mL beaker since, the reaction is quite vigorous and without an adequate beaker, some of the product might spill out and tamper with the results of the experiment.
6. Record the properties of the copper(ii) chloride solution. This will allow one to identify the change in the solution in the reaction and to determine that there is a displacement going on within the reaction. Record this in  “Data Table 1 – Qualitative Data Table” and record it under “Before Reaction”.
7. Ready a Fisher Scientific Hot Plate by setting the knob to 10. This setting signifies approximately 250°C. This high temperature will increase the speed at which the reaction takes place, ensuring that this otherwise slow reaction is completed quickly.
8. Place the copper(ii) chloride solution on this hot plate and then place the aluminum strip in the copper(ii) chloride solution.  Since aluminum is higher on the reactivity series, the aluminum should displace the copper in the solution, creating a reaction. While the reaction is taking place record any quantitative data in “Data Table 1 – Qualitative Data Table” and record it under “During Reaction”. This allows one to sufficiently make a conclusion, based on what is occurring in the reaction.
9. Over the course of the experiment, spray the aluminum strip with water so that any copper lingering on the aluminum is washed down into the solution for filtering in a later step. This will ensure that all the copper is in the solution so that when the solution is later filtered all the copper is there to be massed. This up-keeps the precision of the experiment.
10. When the solution is clear or relatively clear, the reaction has finished taking place and the aluminum strip can be taken out. Since aluminum is the metal in excess, all the copper  (ii) chloride reactant should be transformed in this reaction. This means that when the reaction is finished, there should still be some aluminum since it is excess, and the products should be copper and aluminum chloride. Since aluminum chloride is a clear solution, when the solution turns clear, it indicates that the reaction has finished taking place.
11. Record the properties of the product of the solution to ensure that the reaction is truly finished. Record all these properties in “Data Table 1 – Qualitative Data Table” and record it under “After Reaction”.
12. Take the aluminum strip and wash it to ensure that any remaining copper is washed out and then recycle the aluminum for later usage. This ensures that the aluminum can be used again later in another experiment. Make sure you remove the aluminum with tongs, since the beaker was heated at 250°C.
13. Take a funnel large enough to just fit in a 150mL beaker, the second 150mL beaker and a filter paper small enough to just fit in this funnel. Determine the mass of the filter paper so that the mass of the copper can later be isolated in the calculations. Ensure that step 3 is repeated so that precision of the experiment is being up-kept. Record all this data in “Data Table 2 – Quantitative Data Table” under “Mass of Filter Paper(±0.01g)” . All these materials are required to filter the copper metal out of the aluminum chloride solution.
14. Fold the filter paper into eighths and then unfold it in the shape of the filter paper with a little opening near the bottom of the filter paper. This shape ensures that when the paper is put on the funnel, the copper will stay on the paper, while the solution will drip down into the beaker. Place the filter paper on the funnel and then spray it with water so that it sticks to the funnel. This ensures that when the copper is filtered out, that the filter paper does not move.
15. Pour the product down the funnel and wait for the aluminum chloride solution to filter out to the beaker at the bottom. This effectively isolates the product copper so that it can be massed at a later step. In addition spray the copper with water so that any aluminum chloride clinging to the filter paper gets washed down to the bottom. This better isolates the copper, ensuring precision within the experiment.
16. Take note of the qualitative observations of the copper after filtering out the aluminum chloride and solution. This is to ensure that copper truly is the dry product of the reaction. Record all these properties in “Data Table 1 – Qualitative Data Table” and record it under “After Reaction”.
17. Lay the filter paper out to evaporate out the water on the copper so that the precision of the experiment is being up-kept.  Note that one should only lay it out for approximately twenty-four hours so that the copper does not oxidize. If the copper does oxidize, the mass of the perceived copper would increase and the precision of the experiment would be ruined.
18. After twenty-four hours repeat step 3 and come back and determine the mass of the copper with the filter paper on the OHAUS Precision Standard Weighing balance. This mass will help isolate the mass of the copper in later calculations. Record this mass in “Data Table 2 – Quantitative Data Table” under “Mass of Copper with Filter Paper(±0.01g)”.

Sample Data Table 1 – Qualitative Data Table

Sample Data Table 2 – Quantitative Data Table

Data Collection and Processing

Data Table 1 – Qualitative Data Table

Data Table 2 – Quantitative Data Table

Calculations

Mass of Aluminum Reacted

Moles of Aluminum

Mass of Copper

Moles of Copper

Mole to Mole Ratio of Aluminum to Copper

Converting to a Whole Number Coefficient

Balanced Chemical Equation

Summary Table – Balanced Chemical Equation of the Reaction

Conclusion and Evaluation

Conclusion

The coefficients of a ...