4. A salt solution consisting of 10.0% sodium chloride (salt) consists of how many parts per million (of salt in water)? A. 10 parts per million B. 100 parts per million C. 1,000 parts per million D. 10,000 parts per million E. 100,000 parts per million

18.Which of the following is true? A. When acid is added to pure water, kw, the ion-product constant of water, changes. B. The equilibrium constant of water (keq) is the rate that dissociation of the molecule occurs at room temperature C. The H* (or H³O*) in cells is the same concentration as that of undissociated water D. None of the above E. All of the above

What is the concentration in % (w/v) of a solution prepared from 50.0 g NaCl and 2.5 L of water? A. 5.0 % B. 2.0 % O C. 0.020 % D. 0.050 % E. 0.50 %

3) Which of the following is used to precipitate the nucleic acids Select one O a. Ethanol O b. Glycerol O c. Methanol O d. Ethylene

B

3) Ammonia, NH3, is toxic to a wide range of aquatic organisms including snails, insects, and fish. The ammonium ion, NH4", is much less toxic since the cation does not diffuse rapidly across cell membranes. The US EPA limit for total ammonia in natural waters is 1.9 mg/L at pH 7. a. What is this limit in molar units? b. What is the concentration of NH3 at pH 7? c. What is the concentration of NH3 at pH 6? d. Why is the EPA limit for total ammonia dependent on the water pH?

What is the concentration in % (w/w), of a solution prepared by mixing 50.0 g NaCl and 150.0 g water? A. 0.250 % B. 33.3 % C. 40.0 % D. 25.0 % E. 3.00 %

What is the pH of a cleaning solution with a [H3O*] = 7.4 x 10-10 M H3O*? A. 7.4 B. 9.00 C. 8.13 D. 9.13 E. 7.13

A base a. has a value below 7 on the pH scale. b. is a chemical that adds hydrogen ions to a solution. c. has a value of 7 on the pH scale. d. is a chemical that absorbs hydrogen ions from a solution.

Describe the features of the fluid mosaic model of the cell membrane in detail