Use the following information to answer questions 20-25: Aquariu 7.0 uire a deli

Question

Use the following information to answer questions 20-25: Aquariu 7.0 uire a delicate balance of dissolved gases. A clown fish requires at least survive, but greater than 30.0 ppm of CO2 is toxic. You want to setup a mg/L 20.0 L aquarium t dissolved gases (you've just added the fish, so ignore O2 consumption and O2 to ank at 25.0 °C, where only the atmosphere is responsible for CO2 production). Po0.21 am Pco 0.0039 atm 20. What is the minimum O2 concentration where the fish can survive? A. 2.2x 10 M 21. What is the maximum CO2 concentration where the fish can survive? A. 2.19 x 10-4 M 22. What is the concentration of O2 in the aquarium? A. 9.1 x 104 M 23. What is the concentration of CO2 in the aquarium? A. 5.1 x 10-7 M 24. Can the fish initially survive in the aquarium? A. Yes 25. At what temperature will the concentration of dissolved gases be highest? A. 40 °F B. 0.219 M C. 4.57 M D. 0.011 M B.682 x 10" . 2.19 x 104 M D, 2.19 x 10'4 M B.6.2 x 10-3 M C. 2.7 x 10-4 M D' 1.0 x 10-4 M B. 1.14 M C, 1.3 x 105 M D, 7.0 x 104 M B. No B. 50°F C. 70 F D. 90 °F

Explanation / Answer

20.)

Step 1: Determine the mass of the solute present.

(20 L)(7 mg/L) = 140 mg

Step 2: Convert From mg to g .

140 mg ÷ 1,000 = 0.14 g

Step 3: Convert From g to mol .

(0.14 g) / (32.0 g/mol) = 0.004375 mol [molecular weight of oxygen molecule is 32.0]

Step 4: Calculate the Molarity

0.004375 mol ÷ 20 L = 0.00021875 mol/L = 2.1875 * 10-4 M

Answer: Option A

21.)

Step 0: Convert from ppm to g .

1ppm = 1 mg/L

So, 30ppm = 30 mg/L

Step 1: Determine the mass of the solute present.

(20 L)(30 mg/L) = 600 mg

Step 2: Convert From mg to g .

600 mg ÷ 1,000 = 0.6 g

Step 3: Convert From g to mol .

(0.6 g) / (44.01 g/mol) = 0.0136 mol [molecular weight of oxygen molecule is 44.01]

Step 4: Calculate the Molarity

0.0136 mol ÷ 20 L = 0.000681 mol/L = 6.81 * 10-4 M

Answer: Option B

22.)

Henry's law,

p = Kh * C    [p - partial pressure, Kh - Henry's constant, C - concentration]

C = p / Kh

C = (0.21 atm) / (756.7 atm/ mol/L)

   = 2.775 * 10-4 mol/L

   = 2.775 * 10-4 M

Answer: Option C

23.)

Henry's law,

p = Kh * C    [p - partial pressure, Kh - Henry's constant, C - concentration]

C = p / Kh

C = (0.0039 atm) / (29.76 atm/ mol/L)

   = 1.31 * 10-4 mol/L

   = 1.31 * 10-4 M

Answer: Option C

24.)

Answer: Option A

Explanation: Since the Oxygen level in the aquarium (2.7 * 10-4 M) is greater than the minimum prescribed level (2.2 * 10-4 M), the fish could survive initially. Moreover, Carbon dioxide level in the aquarium is also below the critical limit, hence it is not toxic.

25.)

Answer: Option A

Explanation: solubility of gases decreases with increasing temperature.

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