Mastering chemistry Chapter 10- Google Chrome Secure l httpsi/session masteringc

Question

Mastering chemistry Chapter 10- Google Chrome Secure l httpsi/session masteringchemist next&assignmentProblemID; 76617795 1340 Spring 2017 Section 01 Chaplet 10 Problem 24 What is the H3O' concentration? Problem 24 Express your answer using two significant figures. About 23% of the acid in a 0.10 M solution of a weak acid dissociates to form ions Submit My Answers Grye Up Part B What is the OH concentration? Express your answer using two significant figures. Submit My Answers Give Up Part C What is the pH of the solution? Express your answer using two decimal places. O

Explanation / Answer

a)

Let the acid be HA

HA   +H2O   <—> H3O+(aq)   +   A-(aq)

0.10           0       0   (initial)

0.10-x       x       x   (at equilibrium)

% dissociation = x*100 / initial concentration

23 = x*100/0.10

x = 0.023 M

So,

[H3O+] = x = 0.023 M

Answer: 2.3*10^-2 M

b)

[OH-] = (1.0*10^-14) / [H3O+]

[OH-] = (1.0*10^-14)/(2.3*10^-2)

[OH-] = 4.3*10^-13 M

Answer: 4.3*10^-13 M

c)

pH = -log [H3O+]

= -log (2.3*10^-2)

= 1.64

Answer: 1.64

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