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.