Name: Kamaal Thomas |Date: January 4, 2011 | |Graded Assignment
Lab Report
Answer the questions below. When you have finished, submit this assignment to your teacher by the due date for full credit.
(8 points)
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1. For Part 2: Single-Displacement Reactions: For each of the four single-displacement reactions, describe what happened in each well. If a chemical reaction occurred, write a balanced equation for it. Then using the A, B symbols, write a general equation for a single-displacement reaction.
Here are the chemical formulas of the reactants for each reaction:
• zinc – Zn copper sulfate – CuSO4
In well 1A there was a chemical reaction which turned
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Then using the A, B symbols, write a general equation for a double-displacement reaction.
Here are the chemical formulas of the reactants for each reaction:
• sodium chloride – NaCl copper sulfate – CuSO4
In well 1A there was no chemical reaction between the sodium chloride and copper sulfate. We know this because there was no color change, precipitate formation, or gas production in this mixture.
AX + BY → AY + BX
NO REACTION
• sodium hydroxide – NaOH copper sulfate – CuSO4
In well 2A there was a chemical reaction between the sodium hydroxide and copper sulfate. There was a blue precipitate formation which proves there was a chemical reaction.
AX + BY → AY + BX
NaOH + CuSO4 → NaSO4 + CuOH
• sodium phosphate (trisodium phosphate) – Na3(PO4) copper sulfate – CuSO4
In well 3A there was a chemical reaction between the sodium phosphate and copper sulfate. There was a light blue precipitate formation which proves there was a chemical reaction.
AX + BY → AY + BX
Na3(PO4) + CuSO4 → Na3SO4 + CuPO4
• sodium chloride – NaCl silver nitrate – AgNO3
In well 4A there was a chemical reaction between the sodium chloride and silver nitrate. There was a white precipitate formation which proves there was a chemical reaction.
AX + BY → AY + BX
NaCl + AgNO3 → NaNO3 +
2. Summarize the following description of a chemical reaction in the form of a balanced chemical equation?
These reactions can be seen from just a little bit of reaction all the way up to a complete change of the entire sample tested. Some samples of those tested in this experiment which showed the chemical reaction were the baking soda/ammonia mixture, the Epson salt and baking soda mixture as well as the food coloring mixed with the baking soda and bleach. 2. Which reactions, if any, do you believe showed no evidence of chemical change? Justify your reasoning.
Left with the brown solid formed in the earlier stage add 50 ml of the sulphuric acid given (H2SO4) which is a very corrosive, transparent liquid with no specific odour. The colour changed to teal and the solid dissolved, leaving a teal coloured solution. Once again a chemical reaction occurred, a substance disappeared and the liquid changed colour. The copper is in the solution, the teal colour looks like the originl colour of the copper at the beginning of the experiment
In this experiment an elemental copper was cycled a series of five reactions where it ended with pure elemental copper as well, but at different stages of the cycle the copper was in different forms. In the first reaction, elemental copper was reacted with concentrated nitric acid where copper changed the form from solid to aqueous. Second reaction then converted the aqueous Cu2+ into the solid copper II hydroxide (Cu(OH)2) through reaction with sodium hydroxide. The third reaction takes advantage of the fact that Cu(OH)2 is thermally unstable. When heated, Cu(OH)2 decomposes (breaks down into smaller substances) into copper II oxide and water. When the solid CuO is reacted with sulfuric acid, the copper is returned to solution as an ion (Cu2+). The cycle of reactions is completed with the
In reference to the analysis of anions, Table 1 shows that a precipitate was formed when our unknown was combined with HNO3 and AgNO3, thus indicating the presence of a chloride ion. Because our unknown did not form a precipitate due to HCl and BaCl2, separate, effervesce, or smell, we concluded that neither sulfate, nitrate, carbonate nor
5. Was there any evidence that some of the copper (II) chloride was left in the beaker? Explain.
A chemical reaction is when substances (reactants) change into other substances (products). The five general types of chemical reactions are synthesis (also known as direct combination), decomposition, single replacement (also known as single displacement), double replacement (also known as double displacement), and combustion. In this lab, the five general types of chemical reactions were conducted and observations were taken before, during, and after the reaction. Then the reactants and observations were used to determine the products to form a balanced chemical equation. The purpose of this lab was to learn and answer the question: How can observations be used to determine the identity of substances produced in a chemical reaction?
Conclusion – The main idea of this experiment is that if you have the reactants of a double replacement reaction that you should be able to find out several things. First, you can figure out the products from switching the positive ion with the other positive ion. Once you have found the products you can determine the phase of matter they are in from Table F and H. Finally, you can also determine whether the reaction went to completion or not. The observations and data above leads me to believe that our experiment is valid. We were very careful and observant of the directions that needed to be taken. Once source of error could have been that certain substances were placed in the wrong wells, causing your data to stray from the correct information. One way this experiment could be applied to a real life situation is he residue in the bottom of a glass in your bathroom. There is stuff dissolved in water, and any trace of water left in a glass will eventually evaporate and leave the residue.
Heavy precipitate emerged immediately and solution turned white in color; solution then became opaque and turned light, bright blue in color.
(Hint the concentration of calcium ions in well 12 is 4.9 x 10-5 M.) Place 5 drops of 0.10 M NaOH in each of the wells 1 through 12. When the NaOH is added to each well, the initial concentrations of the reactants are halved, as each solution dilutes the other. Use an empty pipet to mix each of these combined solutions by drawing each solution up into the pipet and squirting it back into the well. (Hint the concentration of Ca2 ions in well 12 is 2.4 x 10-5 M.) Allow three or four minutes for the precipitates to form, then observe the pattern of precipitation. At one point the concentration of both ions becomes too low to have any precipitate form. We will assume that the first well with no precipitate represents a saturated solution. Part B NaOH varies, Ca(NO3)2 held constant To check your results, repeat the procedure but use a serial dilution of the NaOH. In a different row, put 5 drops of 0.10-M NaOH in well 1. Put 5 drops of distilled water in wells 2 through 12. Add 5 drops of the 0.10-M NaOH solution to well 2. Use an empty pipet to mix the solution by pulling the solution into the pipet and then squirting it back several times. The solution in this well, 2, is now 0.050 M in OH- ion. Continue this serial dilution to well 12, and then remove 5 drops from well 12. Add 5 drops of 0.10 M Ca(NO3)2 to each of the wells, and mix each with an empty pipet or stirrer. Again, determine the well where no more precipitate appears. Cleanup
To study the nature of ionic reactions, write balanced equations, and write net ionic equations for precipitation reactions.
The purpose of this experiment is to distinguish the relationships between reactants and products, in addition to expanding on concepts such as single displacement reactions, mole ratio values, moles to mass, theoretical yields, limiting reactants, excess, stoichiometric relationships and percentage errors.
I started with elemental copper metal and then reactions occur step by step as follows:
The lab performed required the use of quantitative and analytical analysis along with limiting reagent analysis. The reaction of Copper (II) Sulfate, CuSO4, mass of 7.0015g with 2.0095g Fe or iron powder produced a solid precipitate of copper while the solution remained the blue color. Through this the appropriate reaction had to be determined out of the two possibilities. Through the use of a vacuum filtration system the mass of Cu was found to be 2.1726g which meant that through limiting reagent analysis Fe was determined to be the limiting reagent and the chemical reaction was determined to be as following:-
From the reactions above, the hydroxide ions (OH-) that will be generated from the compounds will cause a change in pH of the water to becoming more basic. This then causes the Al(OH)3, Fe(OH)2 or Fe(OH)3 to form an insoluble precipitate along with