The dissociation of water into H_3 O^+ and OH^- ions depends on temperature. At

Question

The dissociation of water into H_3 O^+ and OH^- ions depends on temperature. At 0 degree C the [H_3 O^+] = 3.38 times 10^-6 M, at 25 degree C the [H_3 O^+] = 1.00 times 10^-7 M, and at 50 degree C the [H_3 O^+] = 2.34 times 10^-7 M. At what temperature water is acidic? 0 degree C b. 25 degree C c. 50 degree C d. 15 degree C Solubility of NaCI in water in 35.8 g/100 mL of water at 20 degree C. Which one of the following solutions is saturated? a. 35.8 g NaCI/200 mL water b. 50.0 g NaCI/200 mL water c. 20.0 g NaCI/75 mL water d. 53.7 NaCI/150 mL water. An isotonic solution contains 0.15 M NaCI solution? a. 0.15 M CaCI_2 b. 0.10 M CaCI_2 c. 0.05 M CaCI_2 d. 0.45 M CaCI_2 Which compound is copper (II) chloride dihydrate? a. CuCI middot 2 H_2 O b. CuSO_4 middot 2 H_2 O c. CuCI_2 middot 2 H_2 O d. CaCI_2 middot 2 H_2 O Decane is non-polar liquid and has density of 0.730 g/mL. Water has a density of 1.00 g/mL. 5 mL of each of decane and water is transferred to a glass test tube at room temperature. Now 5 mL of saturated iodine-water solution, which has a strong to a glass test tube at room temperature. Now 5 mL of saturated iodine-water solution, which has a strong purple color, is added to the test tube. The test tube is gently shaken and then kept in a test tube rake. Which one of the following observations will hold true? a. The two liquids are immiscible and lower portion of liquid in the test tube will have a strong purple color. b. The two liquids are immiscible and upper portion of liquid in the test tube will have a strong purple color. c. The two liquids are miscible and liquid in the test tube will have a uniform color throughout. d. Decane, water and iodine will form three layers.

Explanation / Answer

Q34.

Theoretically speaking, the solution will neve be acidic, since [H+] = [OH-] always

but in this case, let us assign pH < 7 to be acidic

the only case in which this is true is at high T

pH = -log(H)

pH = -log(2.34*10^-7) = 6.63 at 50°

then, choose C

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