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.