Avi Schafer Stoichiometry Lab SUBMISSION DOCUMENT Assessed Criteria: D (Scientific Inquiry), E (Processing Data), F (Attitudes in Science), B (Communication) Aim: investigate one factor affecting the change in yield of a chemical reaction Instructions Submit work on this document, self-­‐assessed. Use APA citations in-­‐text and references. Include at least 3 reliable external sources. Learn from your previous labs: be organized and self-­‐assess as you go. Write clearly. Follow the guidance. •
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Academic honesty declaration: “I confirm that this work is my own work and is the final version. I have acknowledged each use of the words or ideas of another person, whether written, oral or visual. Although I have worked with a partner on collecting data, all written work and data processing is my own.” Signed: Avi Schafer
Type your name on the line above when the work is complete. Date: 1/22/2013 Criterion D: Scientific Inquiry Self-­‐assess by highlighting statements that best describe your work Level Descriptor 0 1-­‐2 3-­‐4 5-­‐6 The student does not reach a standard described by any of the descriptors below. The student attempts to state a focused problem or research question. The method suggested is incomplete. The student attempts to evaluate the method and respond to the focused problem or research question. The student states a focused problem or research question and makes a hypothesis but does not explain it using scientific reasoning. The student selects appropriate materials and equipment and writes a mostly complete method, mentioning some of the variables involved and how to manipulate them. The student partially evaluates the method. The student comments on the validity of the hypothesis based on the outcome of the investigation. The student suggests some improvements to the method or makes suggestions for further inquiry when relevant. The student states a clear focused problem or research question, formulates a testable hypothesis and explains the hypothesis using scientific reasoning. The student selects appropriate materials and equipment and writes a clear, logical method, mentioning all of the relevant variables involved and how to control and manipulate them, and describing how the data will be collected and processed. The student evaluates the method, commenting on its reliability and validity. The student comments on the validity of the hypothesis based on the outcome of the investigation. The student suggests realistic improvements to the method and makes suggestions for further inquiry when relevant. Page 1 Avi Schafer Criterion E: Processing Data Self-­‐assess by highlighting statements that best describe your work Level Descriptor 0 1-­‐2 3-­‐4 5-­‐6 The student does not reach a standard described by any of the descriptors below. The student collects some data and attempts to record it in a suitable format. The student organizes and presents data using simple numerical or visual forms. The student attempts to identify a trend, pattern or relationship in the data. The student attempts to draw a conclusion but this is not consistent with the interpretation of the data. The student collects sufficient relevant data and records it in a suitable format. The student organizes, transforms and presents data in numerical and/or visual forms, with a few errors or omissions. The student states a trend, pattern or relationship shown in the data. The student draws a conclusion consistent with the interpretation of the data. The student collects sufficient relevant data and records it in a suitable format. The student organizes, transforms and presents data in numerical and/or visual forms logically and correctly. The student describes a trend, pattern or relationship in the data and comments on the reliability of the data. The student draws a clear conclusion based on the correct interpretation of the data and explains it using scientific reasoning. Criterion B: Communication in Science Self-­‐assess by highlighting statements that best describe your work Level Level descriptor 0 The student does not reach a standard described by any of the descriptors below. 1–2 The student uses a limited range of scientific language correctly. The student communicates scientific information with limited effectiveness. When appropriate to the task, the student makes little attempt to document sources of information. 3–4 The student uses some scientific language correctly. The student communicates scientific information with some effectiveness. When appropriate to the task, the student partially documents sources of information. 5–6 The student uses sufficient scientific language correctly. The student communicates scientific information effectively. When appropriate to the task, the student fully documents sources of information correctly. •
Use at least three reliable eternal sources, cited in-­‐text and references, using APA. Criterion F: Attitudes in Science Self-­‐assess by highlighting statements that best describe your work Level Descriptor The student does not reach a standard described by any of the descriptors below. 0 1-­‐2 3-­‐4 5-­‐6 The student requires some guidance to work safely and some assistance when using material and equipment. The student requires some guidance to work responsibly with regards to the living and non-­‐living environment. When working as part of a group, the student needs frequent reminders to cooperate with others. The student requires little guidance to work safely and little assistance when using material and equipment. The student works responsibly with regards to the living and non-­‐living environment. When working as part of a group the student cooperates with others on most occasions. The student requires no guidance to work safely and uses material and equipment competently. The student works responsibly with regards to the living and non-­‐living environment. When working as part of a group, the student cooperates with others. Page 2 Avi Schafer Research Question: “To determine the effect of changing the mass of NaHCO3 on the yield of NaCl by evaporating the product.” Background Balanced equation: HCl(aq) + NaHCO3 (s) NaCl (aq) + CO2(g) + H2O(l) Type of reaction, with reason: •
Define yield. What are some variables you could change in order to affect yield in this reaction? •
Increments: Trials: Mass: 1 0.5 2 1.0 3 2.0 4 4.0 Molar Masses: HCl 36.46g/mol NaHCO3 84.01g/mol NaCl CO2 H2O 58.44g/mol 44.01g/mol 18.02g/mol Variables Independent: NaHCO3 Units & uncertainties (± 0.1) Measured by: Digital balance Reason for By changing the mass, I don’t need that much time and I will be able to work on choosing this: writing. Dependent: NaCl Units & uncertainties (± 0.1) Measured by: Evaporating the product and use the digital balance Hypothesis Predict the effect of your independent variable on the dependent variable For every 84.01g/mol of NaHCO3, 58.44g/mol of NaCl is produced. First, I calculate how many moles of NaHCO3 are going to be used. In order to calculate this, I made a formula of it, 0.5÷84.01=0.006. So, there are 0.006 moles of NaHCO3 are used per 0.5g of NaHCO3. And, when 1 mole of NaHCO3 is produced, 1 mole of NaCl is produced, so when 0.006 moles of NaHCO3 are produced, 0.006 moles NaCl are also produced. So, the moles of NaHCO3 and Page 3 Avi Schafer NaCl are the same. Next, I can calculate the mass of NaCl by making the formula like this, 0.006×58.44=0.35. Mass of NaHCO3 0.5 1.0 2.0 4.0 6.0 Mole of NaHCO3 0.006 0.012 0.024 0.048 0.072 Mole of NaCl 0.006 0.012 0.024 0.048 0.072 Mass of NaCl 0.35 0.70 1.40 2.80 4.20 Changing the mass of NaCl by changing the mass of NaHCO3 mass of NaCl (g) 3 2.5 2 1.5 1 0.5 0 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 mass of NaHCO3 (g) Explain your predictions I think the answer will be like this graph, because when we do the experiment, and when the NaHCO3 reacts, there will be the same moles of NaCl, so I think it will be similar like this. But, I don’t think we will get the same answer, because we can have some mistakes or we can have problem. Page 4 Avi Schafer Experimental Design Controlled Variables Identify Variables Possible impact on results IV; NaHCO3 Mass of NaCl DV; NaCl Mass of NaCl Specific method for control Used digital balance to measure the mass After evaporating, used digital balance to measure the mass Measured by cylinder CV; HCl Left over of NaHCO3 Uncontrollable variables Identify Variables Possible impact on results CO2 Decrease the mass of the product H2O Increase the mass of the product Materials & Equipment 4 Test Tube (100ml ±0.1): Used to measure HCl. 4 Filter and Funnel: Used to separate the left over of NaHCO3 from the product. 4 Petri dish: Used to separate to four different amount of NaHCO3. 4 Beakers (100ml ±1): Used to put the product and the solution in it. 1 Digital balance (±0.01): Used to measure the mass of the product. 1 spoon: Used to scoop NaHCO3. 7.5g of NaHCO3:: The base of the reaction. 100ml of HCl: To react with NaHCO3. Method for manipulating the independent variable We chose 0, 0.5, 1.0, 2.0, 4.0, because if we choose a number like 0.7, then it will be hard to calculate and hard to compare from other number. And the relationships of these numbers are ×2, ×2, 𝑎𝑛𝑑 ×2. So, it’s very easy to compare it. We used spoon to scoop NaHCO3, and put it on the digital balance to measure the mass, and made it to 0.5g, 1.0g, 2.0g, and 4.0g. Method for recording the dependent variable After the reaction, we get NaCl+H2O+CO2, but CO2 is already out of the solution, so in the solution, there are only NaCl+H2O. But, we need to measure the mass of NaCl, so we had it to get out the H2O. In order to do that, we needed to evaporate it. So, we evaporated, and we got NaCl as a left over, and measured that with the digital balance. But, the mass I measured is the mass of NaCl and the beaker. But, I only need the mass of NaCl, so we washed the beaker, and get out the NaCl. And we measured how heavy the beaker is, and we subtracted that from the mass of NaCl and the beaker. Method for collecting sufficient relevant data We should do the experiment again, to make the answer better, but we didn’t have enough NaHCO3 to do the experiment again. Photo or diagram: Page 5 Avi Schafer This picture is about the solution after the reaction. The right beaker is the 0.5g one, and the left beaker is the 1.0g one. This picture is about the solution after the reaction. The right beaker is the 2.0g one, and the left beaker is the 4.0g one. Safety: We didn’t use the safety goggle when we did the experiment. Even when I did the evaporation, I didn’t put the goggle on until Mr. Taylor told me to. So, I can tell that my experiment wasn’t safe enough. Page 6 Avi Schafer Data Collection & Processing Qualitative Data (observations) •
When it reacted, the solution was bubbling, and I think this bubble is CO2, because CO2 is a gas and in this reaction, there is no other gas that could be in the solution. •
When we evaporated the solution, the beakers with 0.5g and 1.0g of NaHCO3, the left over was yellow, because there wasn’t enough NaHCO3 to react all of the HCl. •
When we evaporated the solution, the beakers with 2.0g and 4.0g of NaHCO3, there were a lot of left overs (NaCl) in the beaker. •
When we evaporate the solution, the smell was horrible… Especially, the smell from the beakers with 0.5g and 1.0 g of NaHCO3 were horrible, because we had to much left overs of HCl. Raw Data Increments of the IV (g)(± 0.1)
0.000
0.500
1.000
2.000
4.000
Predicted Yield (g) (± 0.01)
0.000
0.350
0.700
1.400
2.800
Measured Yield (g) (± 0.01)
0.000
0.330
0.580
1.400
2.700
The differnce of predicted tield and measured yield 3 mass of NaCl (g) 2.5 2 1.5 1 0.5 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 -­‐0.5 mass of NaHCO (g ) Predicted Yield Measured Yield Data Processing Our Measured Yield was closer than we thought in the beginning. But, I can say that all of my Measured Yields (beside the 2.0g one) were lower than the Predicted Yield. So, we had an error in the experiment, and some NaHCO3 or some !.!"
NaCl went out from the beaker. And for my 0.5g one, = %, so I had 106.1%, so I had 6.1% of error. And for my 1.0g one, !.!
!.!"
!.!!
= %, so I had 120.7%, so I had 20.7% of error. And for my 2.0g one, I had the same answer as the predicted Page 7 Avi Schafer !.!
yield. And for my 4.0g one, = %, so I had 103.7%, so I had 3.7% of error. According to my calculation, especially my !.!
2.0g one’s error was big. Page 8 Avi Schafer Analysis of Data Description of trends, patterns and relationships First, I can tell that all of the data is increasing and none of them decreased. And Most of my data was lower than the predicted data. And I can tell that I had some mistake in the experiment. Reliability of the data For my data, I don’t think my data has a good reliability. Because, in the experiment, I made many mistake that can affect my data. Especially, when I had too much NaHCO3, and had not enough HCl, I had lots of problem from that. But, even I made mistake, I tried to fix it, and I did things such as measuring the left over of NaHCO3. So, I can’t tell that my data has good reliability enough, but I think it became closer by trying to fix them. Evaluation of the hypothesis My hypothesis was very similar to the result, and that means that our calculations for this was very close to the result. Conclusion First, my research question was “To determine the effect of changing the mass of NaHCO3 on the yield of NaCl by evaporating the product.” And I think I was able to do this by doing the experiment, and calculate it from it. I was able to do this without researching about it, and I think I did this with just thinking by myself, and calculating them. Page 9 Avi Schafer Evaluations Validity of the method I was able to know how the stoichiometry works, and I thought I might be able to use this in the real life. Like, when we don’t have enough water, it might be dangerous, but I can use these chemicals in order to make water. Reliability of the method I had some mistake on this experiment. First, I forgot to calculate how much HCl we needed to react all of the NaHCO3. So, we had some leftover, and that made the experiment complicate. We had it to calculate how much NaHCO3 were left, and in order to get that, we used filter and funnel to separate the NaHCO3 witch is the solid from the solution. So, we had it to do these things. And if we calculate these before the experiment, I think we were able to use our time to write these things, and to be able to success the experiment. Evaluation of specific limitations and sources of error Source of error/ limitation Without calculation at the beginning, and not enough HCl. Did the experiment without putting the safety goggles on. Potential impact on results, with magnitude This made huge impact on our result, because most of our results were lower than the hypothesis. It didn’t effect on our result, but it could be effecting our eyes. Outline a specific method to improve this error/ limitation I can improve by calculating at first, and be preparing for the experiment. Use goggles, and be careful when using chemicals. Suggestions for further inquiry I think I have to calculate before the experiment, and get ready for the experiment. In this experiment, I wasn’t ready, and I just started without knowing the things I should be known. So, for next experiment and lab, I should take time on planning, and get prepare for the experiment. Page 10 Avi Schafer References Nutrlization. (n.d.). Retrieved January 22, 2013, from Virtual Chembook website:
http://www.elmhurst.edu/~chm/vchembook/183neutral.htmlVIRTUAL CHEMBO Page 11