Homework due Wednesday, June 26

25.

A qualitative test is used to identify the presence or absence of a particular substance in a sample (appearance, color, odor, etc) and a qualitative test is used to determine how much of a specific substance is present in a sample.

26.

A confirming test is a positive or negative test that confirms the presence or absence of the ion in question. You should look for a change in the appearance of a precipitate (an insoluble material) to complete this test.

27.

a). The reference solution is a solution where the ion being tested for is present. Typically, when the ion is present in the water sample, the precipitate is weaker because it’s usually present in smaller amounts than in the reference solution.

b). When an ion-stimulating solution is added distilled water, there is no reaction; however, the water remains clear because the distilled water contains no ion.

28.

The student should conclude that no iron is present since there’s no color change. But, technically, the student should conduct further tests because the iron could be present, even if it is very small and unnoticeable.

29.

a). I would stir the mixture and then let it sit to check if any solid particles would settle on the bottom of its container. I could also use the Tyndall Effect to see if it was a colloid.

b). Doing this, I would see if solid particles large enough to settle to the bottom of the mixture are present; therefore, making the mixture an example of suspension.

30.

Since medicine is a colloid, it is not uniform and you might only drink some of the minerals or solutes; thus, you need to shake it.

31.

It is useful for element symbols to have international acceptance because then they can be read by anyone so no confusion will be caused.

32. 

33. 

No because even though there is an expensive process of distillation, you can’t have 100% "chemical free" water. All of the common chemicals (oxygen, carbon dioxide, etc) are always present in water to some extent.

34.

H20 is a liquid made up of gasses; Oxygen and Hydrogen are gasses that turn into a liquid at room temperature.

      Water Testing Lab Questions:

1. The reference solution and a blank were used to compare results.

2. The problems with qualitative tests are that you can see the presence, but you cannot see the amount.

3. If the ions are are present in very small amounts, then the chemical test will not be able to produce a confirming result.

4. If the wells are contaminated, there are results will be unsuccessful.