Question

In the Sherlock Holmes novel (1974) and movie "The seven Per-cent solution" a 7% solution of cocaine (C_17H_21NO_4 303 g/mol) was used. Which of the following ratios would create a 7%" solution? 7 grams of cocaine in 100 mL of water B) 70 grams of cocaine in 1000 mL of water C) 35 grams of cocaine in 465 mL of water D) 21.21 grams of cocaine in 465 mL water E) none of the above Codeine (C_18H_21NO_3, 300g/mol) is a derivative of morphine that is used as an analgesic or antitussive. It tastes very bitter. What is the pH of a 10mL solution containing 5 mg of pure codeine? A) 4.8 B) 1.2 C)6 D)4 E) 9.6 A saturated solution of aspirin (HC_9H_7O_4. 180g/mol contains 3g/L. How would you change 1000mL of a saturated aspirin solution to a 0.01M solution? A) Add 250 mL of water B) heat the solution so the volume decreases to 900mL. Add 0.6 g of aspirin D) add 667 mL of water E)none of the above

Answer 1

53 )

answer : A ) 7 gm in 100 mL water

54 )

moles of codeine = 5 x 10^-3 / 300 = 1.67 x 10^-5

volume = 10 mL = 0.01 L

molarity = C = moles / volume = 1.67 x 10^-5 / 0.01

                = 1.67 x 10^-3 M

pKb of codeine = 6.05

pOH = 1/2 [pkb -logC]

pOH = 1/2 [6.05 - log 1.67 x 10^-3]

pOH = 4.41

pH + POH = 14

pH = 9.6

answer : E ) 9.6