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kotegsom [21]
3 years ago
13

Caffeine (C_8H_10N_4O_2) is a weak base with a K_b value of 4 times 10^-4. The pH of a 0.01 M solution of caffeine is in the ran

ge of: a. 2-3 b. 5-6 c. 7-8 d. 9-10 e. 11-12
Chemistry
1 answer:
docker41 [41]3 years ago
3 0

Answer:

The pH of the solution lies from 11 to 12.Hence, option e is correct.

Explanation:

The value of K_b for caffine = 4\times 10^{-4}

CafOH(aq)\rightleftharpoons Caf(aq)+OH^-(aq)

Initial

   0           0.01 M       0

AT equilibrium:

  x          (0.01 -x)M      x

K_b=\frac{x(0.01-x)}{(x)}

4\times 10^{-4}=\frac{x(0.01-x)}{(x)}

Solving for x:

x = 0.0096 M

The pOH of the solution is given by :

pOH=-\log[OH^-}

pOH=-\log[x]

pOH=-\log[0.0096]

pOH = 2.02

pH= 14 - pOH = 14 - 2.02 = 11.98

The pH of the solution lies from 11 to 12.

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There is some info missing. I think this is the original question.

<em>A chemist dissolves 660.mg of pure hydroiodic acid in enough water to make up 300.mL of solution. Calculate the pH of the solution. Be sure your answer has the correct number of significant digits.</em>

<em />

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