Caribo,James-X03-after-lab

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Bellevue College *

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MISC

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Chemistry

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Feb 20, 2024

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docx

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4

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Chem& 163 X03 Introduction to Acids and Bases Spring 2023 Part A Experimental Determination of Acid Dissociation Constant, Ka Recorded Data: Assigned Acid: Sam- ple M of stock solution M of Pre- pared solu- tion desired V of Pre- pare d so- lu- tion Calculated Volume of Stock solution (To obtain desired M) 1 1M 0.100 90mL 10mL 2 0.1M 0.010 90mL 10mL pH data Sam- ple pH [H 3 O + ] 1 1.30 0.050 2 2.07 8.51*10^-3 0.100 M solution RICES Table Table in units of Molarity Cl2CHCOOH(aq) + H2O (l) -><- Cl2CHCOO- (aq) + H3O+ (aq) 0.1 0 0 -x +x +x 0.1-x X X 0.05 0.05 0.05 K a = ¿ (0.050)^2/0.1-0.050=0.05 2023-04-26 Page 1 of 4 #3308
Chem& 163 X03 Introduction to Acids and Bases Spring 2023 0.010 M solution RICES Table Table in units of Molarity R Cl2CHCOOH(aq) + H2O (l) -><- Cl2CHCOO- (aq) + H3O+ (aq) I 0.010 0 0 C -x +x +x E 0.010-x X X S 0.010 8.51*10^-3 8.51*10^-3 K a = ¿ (8.51*10^-3)^2/(0.010-8.51*10^-3)=0.049 Post-lab questions (for Part A) 1. What is the average experimental value for pKa of your assigned acid based on your two results? Do your two values agree with each other? Is this what you expected? Why or why not? The two values agree with each other as they were practically the same. This makes sense and is expected because the ratio remains the same and doesn’t affect the Ka. 2. Compare the literature value of your assigned acid to your experimental value. Provide a citation for your source of the literature value of pKa. What sources of error can you identify (be specific – don’t just say “mea- suring errors” only YOU can prevent measuring errors!) Maybe the molarity of the stock solution could have been messed up without knowing. 3. What is the total % dissociation of HA for the 0.10 M sample? _____ __50%_ ______ 2023-04-26 Page 2 of 4 #3308
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