California State Universi X O ming-Com view.php?id 35068000 6/13/2017 11:00 PM D

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California State Universi X O ming-Com view.php?id 35068000 6/13/2017 11:00 PM Due Date: Map General Chemistry 4th Edition University Science Books Points Possible: 10 presented by Saping Learning Grade Category: Graded Calculate the pH of the resulting solution if 20.0 mL of 0.200 M HCI(aq) is added to Description Policies: CHEM215 01 (a) 25.0 mL of 0.200 M NaOH (aq). Number You can check your answers. pH You can view solutions when you complete or g up on any question. You can keep trying to answer each question un (b) 30.0 mL of 0.250 M NaOH (aq). you get it right or give up Number You lose 5% of the points available to each ans pH answer question for each incorrect attempt at t n your o eTextbook O Help With This Topic o Web elp & Videos o Technical Support and Bug Reports Previous Give Up & View solution Q Check Answer C Next Exit 2011-2017 Sapling Learning Inc. about us Careers privacy policy terms of use contact us help 705 PM M I'm Cortana. Ask me anything 613/2017

Explanation / Answer

HCl is a strong acid and it ionizes completely. The number of moles of HCl present in 20 mL 0.2 M HCl is = (0.2/1000) *20 = 0.004 moles (since Molarity is the number of moles of solute in 1000 mL)

a) NaOH is also a strong base it ionizes completely.

NaOH + HCl gives NaCl + H2O

25 mL 0.2M NaOH contains

(0.2/1000) * 25 = 0.005 moles

As per above eqaution one mole HCL rects with 1 mole NaOH

Thus solution contains 0.001 moles NaOH in 45 mL

on converting to molarity = (0.001/45)*1000 = 0.022 M

pOH = -log [0.022] = 1.65

pH = 14 -pOH = 14-1.65 = 12.35

b) 30 mL 0.25 M NaOH

contains (0.25/1000) *30 = 0.0075 moles

and the solution contains only 0.004 moles of HCl.

Thus 0.0035 moles NaOH will be there in the solution of 50 mL

Converting to Molarity'

(0.0035/50)*1000 = 0.07 M

pOH = -log [0.07] = 1.154

pH = 14 -pOH = 14-1.154 = 12.846

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