Homework Assignment 10

ISCS #9-19 p. 82-83

9. 20% of 55 = 11g (mass of sugar) -- 55 - 11 = 44g (mass of water)

10. 0.0015 x 1,000,000 = 1500 ppm

11. A water molecule is polar because each one contains 1 oxygen atom, which is negative, and 2 hydrogen atoms, which are positive. Since these are opposites, they attract, bringing the H2O molecule together.

12. Water molecules arrange themselves relative to one another.

13. 

• a. O-
• b. H+

14. Heavy metals are called heavy because their atoms have greater masses than those of essential metallic elements.

15. 3 symptoms of heavy metal poisoning are damage to the nervous system, brain, kidneys, and liver, which can sometimes lead to death.

16. Two possible sources of human exposure to:

• a. Lead
• Water transported through lead pipes
• Automobile electrical storage batteries
• b. Mercury
• Medical and weather thermometers
• Fluorescent light bulbs

17. Hydrogen ions are found in many bases.

18. The element hydrogen is found in most acids.

19. Acidic, basic, or neutral?

• a. basic
• b. basic
• c. acidic
• d. neutral

ISCS #20-27, 33, 35

20. Which is more acidic?

• a. tomato
• b. black coffee
• c. milk of magnesia

21. 20 times more acidic

22. 3 negative effects of inappropriate pH levels on aquatic organisms:

• Fish-egg development is impaired
• Fish cannot reproduce
• Fish are intoxicated when aluminum ions are present in sufficiently high concentration

23. Polar molecules have different charges at each end (one is positive and one is negative). Non-polar molecules do not have these different charges at each end. Also, polar molecules dissolve in polar molecules, but non-polar molecules do not dissolve well in polar molecules.

24. I would choose lamp oil to dissolve a non-polar molecular substance because non-polar molecules do not dissolve well in ethanol or water (since those solutions are polar).

25. Table salt will dissolve in water, but not cooking oil since it is polar and cannot dissolve well in the oil.

26. The phrase "like dissolves like" explains how polar solutes dissolve well only in polar solvents. Likewise, non-polar solutes dissolve well only in non-polar solvents. So, a polar solute would not dissolve well in a non-polar solvent, and a non-polar solute would not dissolve well in a polar solvent.

27. You cannot satisfactorily clean greasy dishes with just plain water because water is polar, whereas grease is non-polar. The two substances do not dissolve each other completely and cannot completely clean the dishes in a fulfilling way.

33. 

• a. Materials found in these waterless hand cleaners: non-polar molecules
• b. These cleaners are more effective than washing with water because they are capable of dissolving grease easier due to the phrase "like dissolves like".

35. In HF, I would expect Hydrogen to have a partial positive charge because the electron density would be larger than Fluorine's.

Blog Question

Explain how the solubility curve lab works.
The solubility curve lab begins with collecting experimental data to construct a solubility curve for succinic acid, a molecular compound. First, you fill a beaker with water and heat it. Then, place succinic acid in 2 test tubes, adding 20 mL of distilled water to each. Place the test tubes inside of the beaker with warm water, carefully stirring the succinic acid solutions. Pour only the clear liquid from the solutions into separate, clean test tubes and then place those into an ice bath, stirring the liquid gently once or twice. Tap the side of each test tube, which then causes the crystals to settle at the bottom. Measure the height of the crystals and compare results. Lastly, submit your data. 

Blog Question

Explain how to do solution concentration problems. What is the tricky part?

When solving solution concentration problems, you must first create or observe a solubility curve graph. Then, the tricky part comes in when calculating the percent of mass.

Homework Assignment 9

C.5 #1-3 p. 62

1. 

• a. The solution goes from being unsaturated to saturated.
• b. 
  

2.

• a.  
  
  
  
  
  
  
  
• b. 
• i. 
  
• ii. 20 g

3. 

• a. 
  
  
  
  
  
• b. 
  
• c. The models in 3a and 3b are different because the one in 3b is less concentrated. The molecules are more spread out as a result of the additional water that was added, whereas in 3a, there is less water and the KCl molecules are closer together.

Blog Question

Explain your way of solving math word problems when answering solubility questions.

By using the graph of solubility at certain temperatures, I can answer many questions much easier. I follow the lines of each solution and then observe how hot or cold a specific volume of the solvent must be in order for the solute to dissolve.

Homework Assignment 8

C.2 #1-3 p. 56

1. 

• a. 108 g
• b. 45 g

2. 

• a. 10 g
• b. 20 g

3. 

• a. 87.5 g will precipitate
• b. 80 g

ISCS #1-8 p. 82

1. Three teaspoons of sugar will dissolve in hot tea, but not equally in iced tea because the differences in temperatures can affect the solubility.

2. 47 g

3. Solubility of sugar

• a. 200 g
• b. 710 g
• c. 1892 g

4. Most to least soluble

• a. 20 degrees C: NaCl, KCl, KNO3
• b. 80 degrees C: KNO3, KCl, NaCl

5. The term saturated means a solution in which the solvent has dissolved as much solute as it can retain at a specific temperature. The term unsaturated means a solution containing a lower concentration of solute than a saturated solution contains at a specific temperature.

6. Solubility of potassium nitrate

• a. 35 g
• b. saturated
• c. 90 g

7. 

• a. Unsaturated: the crystal will dissolve.
• b. Saturated: the crystal will form at the bottom.
• c. Supersaturated: the crystal will add to the precipitate at the bottom.

8. 40% ethanol

Blog Question

What did you learn from this lab about water and about the process?

I learned that even through many purification processes and tests to check the presence of various ions, it is impossible to make water entirely chemical free. Many atmospheric gasses always manage to maneuver into the water, thus making water never completely pure.

Homework Assignment 7

ISBS #25-34 p. 51-52:

25. Qualitative tests deal with identifying the presence or absence of a particular substance in a sample. Quantitative tests determine the amount of a specific substance present in a sample.

26. A confirming test is a positive test confirming that the ion in question is present.

27. Purpose of...

• a. Reference solution: used to compare with other solutions and try to figure out what substances exist
• b. Distilled-water blank: used to compare with other solutions because usually when certain ions are present, there is no significant reaction

28. If when a student tests a sample of groundwater for iron and observes no color change, then the student should not conclude that no iron is present. This is because iron particles could be so small and barely visible, so any complete conclusion may be false.

29. Given and unknown mixture,

• a. I would classify the mixture as a solution, suspension, or colloid by mixing it and observing the effects, using the Tyndall Effect, and then attempting to purify it through the various processes we learned.
• b. Each step would help me to distinguish among the three types of mixtures. First, the mixing process would allow me to identify a suspension (if the particles separated and solids sunk). Second, the Tyndall Effect would allow me to identify a colloid. After the purification process, if I was still unsure about my results, then the mixture would have to be a solution.

30. The possible risks in failing to follow the direction to "shake before using" on the label of a medicine bottle are not getting the full amount of medicine. Many of the larger particles would sink to the bottom and not be evenly spread throughout the medicine bottle. 

31. It is useful for element symbols to have international acceptance because people of many different countries and backgrounds can obtain a common knowledge of science.

32. Solution where water is a solvent and oxygen is the solute:

33. It is not possible for water to be 100% chemical free because there will always be some gasses from the air that manage to get into the water.

34. A physical property of water is that it is a liquid with a freezing/melting point of 0 degrees C and a boiling point of 100 degrees C. The elements that it is made of (hydrogen and oxygen) are both gasses that do not consist of the same freezing/melting/boiling points.

Water Testing Lab Report

Water Testing Lab

June 25, 2013

Juliet, Rio, Nora

Dr. Forman

Purpose: To test for the presence of iron and calcium cations as well as chloride and sulfate anions.

Background/Significance: After testing various water samples in order to discover the presence of certain cations and anions, we have learned how to distinguish qualitative and quantitative properties. By doing this, we have also reached conclusions about the water samples that we would not have known before.

Abstract: In this experiment, we underwent various procedures in order to test for some cations and anions. From these processes, we have taken many valuable lessons. First, we learned that we must be careful and thorough if we hope to attain the correct results and complete our work efficiently and successfully. Second, we had to wash all of our materials not only to maintain a clean working environment, but also to achieve the qualitative data that we strived for. After attaining the results that we desired, we were able to discover what substances pollute our water.

Procedure:

Calcium Ion (Ca²⁺) Test

1. Place 20 drops of each sample (distilled water, reference, unknown, tap water, natural water) in a well plate
2. Add 3 drops of sodium carbonate to each sample and record your observations
3. Discard the contents and rinse the well plate

Iron (III) Ion (Fe³⁺) Test

1. Place 20 drops of each sample (distilled water, reference, unknown, tap water, natural water) in a well plate
   
2. Add 2 drops of potassium thiocyanate to each sample and record your observations
   
3. Discard the contents and rinse the well plate

Chloride Ion (CI^-) Test

1. Place 20 drops of each sample (distilled water, reference, unknown, tap water, natural water) in a well plate
2. Add 3 drops of silver nitrate to each sample and record your observations
   
3. Discard the contents and rinse the well plate

Sulfate Ion (SO₄^2-) Test

1. Place 20 drops of each sample (distilled water, reference, unknown, tap water, natural water) in a well plate
2. Add 3 drops of bacterium chloride to each sample and record your observations
   
3. Discard the contents and rinse the well plate

Results: From these experiments, our group obtained interesting data; some was correct, while others had errors along the way. After testing all of the samples for the presence of the calcium ion, iron ion, chloride ion, and sulfate ion, most of our results seemed reasonable; however, we did make one vital mistake. During the chloride ion test, when we were examining the distilled water, we received a reaction that turned out to be blue. After redoing the procedure and checking our work, we found a mistake and ended up with a clear sample that did not actually have a reaction. This was probably because we did not completely clean our materials and therefore, chemicals got mixed, causing a different appearance for the sample.

Calcium Ion (Ca²⁺) Test

Solutions	Observations	Results
Reference:	Cloudy with precipitate	Yes
Control:	No reaction, clear	No
Tap water:	No reaction, clear	No
Natural (ocean) water:	No reaction, clear	No
Distilled (blank) water:	No reaction, clear	No

Iron (III) Ion (Fe³⁺) Test

Solutions	Observations	Results
Reference:	Blackish, bloody, brownish red color	Yes
Control:	No reaction, clear	No
Tap water:	No reaction, clear	No
Natural (ocean) water:	No reaction, clear	No
Distilled (blank) water:	No reaction, clear	No

Chloride Ion (CI^-) Test

Solutions	Observations	Results
Reference:	White	Yes
Control:	White	Yes
Tap water:	Yellow	Yes
Natural (ocean) water:	Bluish, purple	Yes
Distilled (blank) water:	Clear (error – on our first try, it turned blue)	No

Sulfate Ion (SO₄^2-) Test

Solutions	Observations	Results
Reference:	No reaction, clear	No
Control:	Blue	Yes
Tap water:	Bluish, clear	Yes
Natural (ocean) water:	No reaction, clear	No
Distilled (blank) water:	Cloudy white	Yes

Class Data Results:

		H	He	Li	Be	B	C
Ca Test	Control	No	No	No	No	No	Yes
	Ocean	Yes	Yes	No	No	No	No
Fe Test	Control	Yes	Yes	No	No	No	No
	Ocean	No	No	No	No	No	No
Cl Test	Control	Yes	Yes	No	No	Yes	Yes
	Ocean	Yes	No	Yes	Yes	Yes	Yes
Sulfate Test	Control	Yes	Yes	Yes	Yes	Yes	Yes
	Ocean	Yes	Yes	Yes	Yes	Yes	Yes

Lab Questions #1-4 p. 45:

1. A reference solution and a blank were used in each test in order to compare the other samples with simpler ones.
2. The qualitative tests may easily be affected by not cleaning the well plate or pipet thoroughly. As a result, the correct reactions may not occur, leading to an error and a misconception of the final conclusion.
3. These tests cannot absolutely confirm the absence of an ion because many times, one cannot see the ions with the naked eye; therefore, the final result is nearly impossible to figure out when a substance is not completely visible.
4. Our observations might have changed if we had not cleaned our wells or stirring rods thoroughly after each test. Incorrect colors and reactions would be formed as a result of incorrect chemicals mixing.