(A) if both sentences are true, (B) if both sentences are false, (C) if the first sentence is true but the second is false, and (D) if the first sentence is false but the second is true. 1. Insufficient dissolved oxygen is necessary for the life of fish and other aquatic organisms. As aquatic photosynthesis is light dependent, the dissolved oxygen produced will peak during daylight hours and decline at night. 2. The solubility of oxygen in water increases at colder temperatures, and decreases at higher temperatures. DO can be measured in milligrams of oxygen (O2) per liter of water. 3. The ideal electrical conductivity of totally pure water is 0.055 microSiemens, whereas typical deionized water has an electrical conductivity of 0.1 microSiemens. The freezing point of water at 1 atm is 100degC.
(A) if both sentences are true,
(B) if both sentences are false,
(C) if the first sentence is true but the second is false, and
(D) if the first sentence is false but the second is true.
1. Insufficient dissolved oxygen is necessary for the life of fish and other aquatic organisms. As aquatic photosynthesis is light dependent, the dissolved oxygen produced will peak during daylight hours and decline at night.
2. The solubility of oxygen in water increases at colder temperatures, and decreases at higher temperatures. DO can be measured in milligrams of oxygen (O2) per liter of water.
3. The ideal electrical conductivity of totally pure water is 0.055 microSiemens, whereas typical deionized water has an electrical conductivity of 0.1 microSiemens. The freezing point of water at 1 atm is 100degC.
4. When water is mixed with metals, a metal hydroxide is formed and oxygen gas is evolved. The evolution of the oxygen gas from the reaction of metals and water is indicated by the hastened consumption of the splinter.
5. Carbon dating is an application of nuclear chemistry where they use the amount of C-14 in a fossil to determine its age. Nuclear power plants produce radioactive wastes.
6. When water is mixed with oxides, hydrogen gas is evolved. A red to blue color change in the litmus paper indicates that the solution tested is an acid.
7. In the Winkler Titration Method, sodium thiosulfate is standardized against a known concentration of magnesium iodate. The normality (N) of a solution is always equal to its molarity (M).
8. In the experiment on determining the dissolved oxygen concentration of a water sample, the compound used to acidify the sample was hydrochloric acid. An acidic solution will have a pH greater than 7.
9. Radioactive wastes, like uranium, must be handled and disposed of according to special regulations designed to protect people and the environment. Nuclear power plants produce too much greenhouse gases due to the burning of uranium.
10. In the Winkler Titration Method, the starch solution turns colorless in the presence of free iodine in the solution to be titrated. In the Winkler Titration Method, the endpoint is determined by the visual indicator, methyl violet.
11. Radioactive elements gain stability by single emission, and a successive emission creates a series. Half-life is the half of the amount of life that a radioactive material will continue to exist before it decays completely.
12. In collecting the tap water sample used in the experiment on dissolved oxygen determination, the container was allowed to overflow so that no bubbles will be formed inside the container that may affect the amount of DO in the water sample. In the experiment on dissolved oxygen determination, the tips of the pipettes should be well above the surface of the liquid when introducing various reagents into the full bottle of sample.
13. The potability or “drinkability” of tap water varies from place to place. The distillation process ensures that contaminants are left in the boiling vessel, which results in a cleaner and more pure water in the collection vessel.
14. The filtrate in any filtration process is left on the surface of the filter paper, while the residue is collected at the bottom of the flask/container after passing through the filter paper. In the distillation process, the methyl violet served as a compound to acidify the water.
15. The stable form of oxygen in the Winkler Titration Method in determining the dissolved oxygen in water was magnesium dioxide. The free iodine in the Winkler Titration Method turned the solution into a red color.
16. The addition of salt in the distilling mixture made the water impure and saline. The addition of 5 drops of the silver nitrate solution into the distillate determines whether the distillate is impure or pure water.
17. In the distillation process, the absence of a reaction when the distillate is mixed with the silver nitrate solution indicates that the distillate is impure water. In a simple distillation set-up, the cooling water exits at the bottom part of the condenser.
18. When a non-metallic oxide reacts with water, a base will be formed as the product of the reaction. When a metallic oxide like phosphorous pentoxide reacts with water, a base will be formed as the product of the reaction.
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