Homework 6/25/13

25. Qualitative tests identify the presence of absence of a particular substance in a sample while a quantitative test determines the amount of a specific substance present in a sample.

26. A confirming test is a positive test that confirms that the ion is question is present. In each confirming test, you look for a change in solution color or for precipitate. 

27. 
a. The reference solution is a solution where the ion being tested for is present; therefore, it is an example of what the precipitate looks like when the ion is present in the water sample. 
b. Since the distilled-water lacks all ions, it shows that when an ion-stimulating solution is added to it, there is no reaction, but the water remains clear instead. 

28. If a student is testing a sample and the student observed no color change, there could still be ions present just in small quantities. Therefore, the student should not conclude that no ions are present. 

29. 
a. I would stir the mixture and wait for a bit to see if any particles settle on the bottom. I would also use the tyndall effect. 
b. I would stir the mixture to see if any particles are large enough to settle on the bottom because then I would know that the mixture is a suspension. I would use the tyndall effect because it would tell me that with a positive tyndall effect, the mixture is a colloid or a suspension but with a negative effect, the mixture is a solution. 

30. If one does not shake the bottle like the directions say, the large particles would stay settled in one part of the bottle and the mixture would not be uniform throughout. Therefore, the individual would not make use of the medicine because without these essential particles, the intended effect would not happen. 

31. It is useful for element symbols to have international acceptance so that scientists all around the world regard elements the same and it is easier for them to deal with these elements. 

32. 

33. Water can never be 100% chemical free, or pure. Water always contains dissolved minerals and gasses that cannot be removed. 

34. Water is made out of two hydrogen atoms and one oxygen atom. Also, water has a high surface tension but hydrogen and oxygen do not have high surface tensions. While water has a boiling point of 100 degrees celsius, a freezing point of 0 degrees celsius, and densities of 1g/ml and 1g/cm cubed, hydrogen and oxygen have different freezing points, melting points, and densities.