The Determination of a Chemical Formula Lab Report

Results:

Table 1: Mass of all substances and tools used in the lab.

Table 2: Qualitative Observations

Data Analysis:

1. There were 0.01332 moles of water in my sample of copper chloride hydrate. The first step that I took to find this answer was adding 1.008g+1.008g+15.999g because 1.008 is the mass of hydrogen, and 15.999 is the mass of oxygen, and adding two hydrogen and one oxygen will give me the total mass of water. I got an answer of 18.015g. Then I divided 0.24g÷18.015g to find how many moles were in my sample. I did this because 0.24g is the amount of water that I determined was in my sample, and dividing that by the weight of water will provide the amount of moles in my sample. My answer was 0.01332 moles.  

2. There were 0.00802 moles of copper in my sample of copper chloride hydrate. To find this answer, I did this math: 0.51g ÷ 63.55g. I did this because 0.51g was the amount of copper that I found in my sample, and dividing it by 63.55g, the mass of copper determines the amount of moles of copper in my sample of copper chloride hydrate.  

3. There were 0.00733 moles of chlorine in my sample of copper chloride hydrate. To find this answer, I did the following math: 0.26g ÷ 35.45g because 0.26g is the amount of chlorine that I found in my sample, and dividing it by 35.45g, which is the mass of chlorine, will determine the moles of chlorine present in my sample of copper chloride hydrate.    

4. The ratio of moles of copper to moles of water for my sample of copper chloride hydrate is 0.00802 : 0.01332 which can be simplified to a whole number ratio of 1:2. To find this whole number ratio, I divided all of the answers in moles by the moles of chlorine, 0.00733 moles because it is the smallest. That made chlorine 1, copper 1, and water 2. Now all three are whole numbers, and the ratios are much simpler.

5. The ratio of moles of copper to moles of chlorine in my sample of copper chloride hydrate is 0.00802 : 0.00733 which can be simplified to a whole number ratio of 1:1. To find this, I used the numbers that I had already determined from question 4, and used them for this question.    

6. The chemical formula for my sample of copper chloride hydrate would be CuCl · 2H₂0. I found this using the whole numbers that I determined in question 4. I divided each answer from questions 1, 2, and 3 in moles by 0.00733 moles, because it was the smallest number, which created numbers close to whole numbers, and then I rounded to create whole number ratios for each ingredient. Both copper and chlorine were 1, and water was 2. Then I plugged these into the formula, and got my answer.

Post-Lab Questions:

1. We can we identify the chemical formula for the compound by comparing the ratio of moles instead of needing to compare the ratio of atoms because if you calculate correctly, the moles are the same ratio to the atoms. You aren't actually changing any data when converting to a different unit. It is helpful to convert to moles because atoms are very small and it is difficult to work with them, so it makes it easier to do calculations when you convert to moles.    

2. When I research the compound CuCl · 2H₂0 , which I determined from my data, there are no results. It always corrects to CuCl₂ · 2H₂0, which is the correct formula for copper chloride hydrate. The formula that my data yielded is slightly incorrect due to errors in the experiment that I performed. When I look at the pictures of the correct formula, CuCl₂ · 2H₂0, it appears the same as the substance we used in the experiment.    

3. The evidence that I have from my experimentation proving that the substance I initially started with was a compound is the fact that we were able to seperate it out into three separate parts: two elements and one compound. Originally, the substance was one material and we chemically separated it into different elements, and the definition of a compound says that it is made up of two or more elements. This compound was made up of four elements: copper, chlorine, hydrogen, and oxygen.    

4. My mole ratios did not come out to perfect whole number ratios. I think that the ratios came out like they did because my partner and I made some errors throughout the experiment. We lost some of our copper because we put the wire into a graduated cylinder instead of a beaker and it was difficult to get out, so we lost some copper mass during that process. We also didn’t dry the copper all the way because we ran out of time, which made it heavier, which most likely skewed our results for all of our data.

5. A scientific theory explains and predicts a phenomenon, so a theory's role in interpreting data is to predict and explain how and why the experiment happens. An expectation can also have an effect on data because if you have certain expectations, they can interfere with how you conduct and interpret the experiment. I think it was reasonable to round off the mole ratios and presume the data should be seen as whole number ratios because as long as the numbers were close to a whole number, that is most likely what it was supposed to be, and the data will not change from slight rounding, and whole numbers are much easier to work with than large decimals.  

6. One possible error a student group might have made in the experiment that would have altered their final results is not drying the recovered copper all the way.  

1. This error would have affected the mass of copper and chlorine recovered, but not water. It would not have affected the mass of water recovered because the mass of water was determined before the error occurred. It would have made the mass of the copper higher than it should have been, which would have skewed the mass of chlorine because we found the mass of chlorine based on the mass of copper.    
2. This error could have altered the first part of the chemical formula determined because that part includes copper and chlorine, but the second part of the formula would not have been affected because the mass of the water was not affected. The chemical formula could have increased amounts of copper and decreased amounts of chlorine, but it would have the same numbers for water.