Preview of “Lab 10 InLab - Acid-Base Studies”

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Unformatted text preview: 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies WebAssign Lab 10 InLab -­ Acid-­Base Studies (In-­Lab) Current Score : 50 / 50 Steve Yarush CH102, section 021, Fall 2012 Instructor: Brandon Zoellner Due : Tuesday, November 6 2012 05:25 PM EST The due date for this assignment is past. Your work can be viewed below, but no changes can be made. Important! Before you view the answer key, decide whether or not you plan to request an extension. Your Instructor may not grant you an extension if you have viewed the answer key. Automatic extensions are not granted if you have viewed the answer key. Request Extension View Key -‐‑Responses/last?dep=4450437 1/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies 1. 7.5/7.5 points | Previous Answers NCSUGenChem102LabV1 10.IL.01. Part A: pH Measurements of Some Common Acid and Base Solutions Complete the following table. (Enter your pH values to the 0.1 place.) Data Table A: pH measurements of acids and bases commonly found in a chemistry laboratory. number solution pH 1 0.010 M HCl 2.2 2 0.0010 M HCl 3.0 3 0.00010 M HCl 4.0 4 0.010 M HC2H3O2 3.5 5 0.010 M NaOH 12.0 6 0.0010 M NaOH 10.5 7 0.010 M NH3 10.2 Recall from your lab manual that [H3O+ ] = 10−pH and that Kw = [H3O+ ] · [OH – ] = 1.0 10−14. Using your measured pH values, calculate the [H3O+ ] and [OH – ] for solutions 1, 4, 5 and 7. (Enter all calculations to two significant figures. Very small and very large values should be entered using scientific notation. For example, 0.000163 should be entered as 1.6e-­4.) number solution [H O+ ] [OH‾ ] 1 0.010 M HCl 6.3e-­3 1.6e-­12 4 0.010 M HC2H3O2 3.2e-­4 3.1e-­11 5 0.010 M NaOH 1.0e-­12 1.0e-­2 7 0.010 M NH3 6.3e-­11 1.6e-­4 3 Acid-­Base Studies -‐‑Responses/last?dep=4450437 2/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies 2. 6/6 points | Previous Answers NCSUGenChem102LabV1 10.IL.02. Green checks and red X's are not displayed for this question. In-­Lab Question 1. Comparing the concentration of your solutions with the hydronium or hydroxide concentration, select the response that is suggested by your pH measurements. (a) For solution 1, the [HCl] is approximately equal to a strong acid and that K >> 1 . (b) For solution 4, the [HC2H3O2] is much greater than HC2H3O2 is a weak acid and that K << 1 and that K >> 1 and that K << 1 [OH – ], suggesting that . (d) For solution 7, the [NH3] is much greater than weak base [H3O+ ], suggesting that . (c) For solution 5, the [NaOH] is approximately equal to NaOH is a strong base [H3O+ ], suggesting that HCl is [OH – ], suggesting that NH3 is a . Acid-­Base Studies -‐‑Responses/last?dep=4450437 3/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies 3. 1.5/1.5 points | Previous Answers NCSUGenChem102LabV1 10.IL.03. Green checks and red X's are not displayed for this question. In-­Lab Question 2a. What happened to the pH when the 0.010 M HCl was diluted to 0.0010 M HCl? It increased. It decreased. It did not change. In-­Lab Question 2b. What happened to the pH when the 0.010 M NaOH was diluted to 0.0010 M NaOH? It increased. It decreased. It did not change. In-­Lab Question 2c. State a general rule about what happens to the pH of acidic or basic solutions when they are diluted with pure water. Diluting a strong acid results in a lower concentration of hydronium, which decreases the pH. Diluting a strong base results in a lower concentration of hydroxide, which increases the pH. Diluting a strong acid results in a lower concentration of hydronium, which increases the pH. Diluting a strong base results in a lower concentration of hydroxide, which decreases the pH. Diluting a strong acid or base will always result in a decrease of the pH. Diluting a strong acid or base will always result in an increase of the pH. Diluting a strong acid or base does not change the pH at all because these materials dissociate completely. Acid-­Base Studies -‐‑Responses/last?dep=4450437 4/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies 4. 9/9 points | Previous Answers NCSUGenChem102LabV1 10.IL.04. Green checks and red X's are not displayed for this question. Part B: Acidity and Basicity of Some Household Chemicals Complete the following table. (Enter your pH values to the nearest whole number.) Data Table B: Acidity and basicity of some household chemicals substance pH acid/base/neutral vinegar 3 acidic bleach 8 basic vitamin C 3 acidic lemon juice 2 acidic baking soda 11 basic dishwasher detergent 9 basic carbonated water 6 acidic baking powder 11 basic ammonia 12 basic Acid-­Base Studies -‐‑Responses/last?dep=4450437 5/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies 5. 1.5/1.5 points | Previous Answers NCSUGenChem102LabV1 10.IL.05. In-­Lab Question 3a. Select all of the household chemicals that you found to be acidic. (Select all that apply.) ammonia baking powder baking soda bleach carbonated water dishwasher detergent lemon juice vinegar vitamin C none In-­Lab Question 3b. Select all of the household chemicals that you found to be basic. (Select all that apply.) ammonia baking powder baking soda bleach carbonated water dishwasher detergent lemon juice vinegar vitamin C none In-­Lab Question 3c. Select all of the household chemicals that you found to be neutral. (Select all that apply.) ammonia baking powder baking soda bleach carbonated water dishwasher detergent lemon juice vinegar vitamin C none Acid-­Base Studies 6. 4/4 points | Previous Answers NCSUGenChem102LabV1 10.IL.06. For Data Table B, the pH of baking soda (sodium bicarbonate) was measured. Answer the following questions based on your observations. (Use the lowest possible coefficients. Include -‐‑Responses/last?dep=4450437 6/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies states-­of-­matter under the given conditions in your answer.) (a) Write the dissolution reaction for solid sodium bicarbonate below. NaHCO3(s) → Na+(aq)+ HCO3-­(aq) NaHCO_3(s) -‐‑-‐‑> Na^+(aq)+ HCO_3^-‐‑(aq) Once the ionic solid has dissolved, the amphiprotic anion that is formed is able to react as an acid or as a base with water. (For parts b and c, omit states-­of-­matter in your answer.) (b) Write the acid-­base reaction where hydrogen carbonate is the acid and water is the base. HCO3-­+H2O → CO 2-­ 3 + H3O+ HCO_3^-‐‑+H_2O -‐‑-‐‑> CO_3^2-‐‑ + H_3O^+ (c) Write the acid-­base reaction where water is the acid and hydrogen carbonate is the base. H2O + HCO3-­ → OH-­ + H2CO3 H_2O + HCO_3^-‐‑ -‐‑-‐‑> OH^-‐‑ + H_2CO_3 (d) Based upon the pH you measured, which statement is accurate? The reaction of hydrogen carbonate as an acid with water is more extensive because the measured pH is greater than 7. The reaction of hydrogen carbonate as a base with water is more extensive because the measured pH is less than 7. The reaction of hydrogen carbonate as a base with water is more extensive because the measured pH is greater than 7. The reaction of hydrogen carbonate as an acid with water is more extensive because the measured pH is less than 7. Acid-­Base Studies -‐‑Responses/last?dep=4450437 7/8 12/5/12 Lab 10 InLab -‐‑ Acid-‐‑Base Studies 7. 5.5/5.5 points | Previous Answers NCSUGenChem102LabV1 10.IL.07. Part C: Acid-­Base Reactions Write the acid-­base reaction that occurs when an aqueous solution of HCl is added to an aqueous solution of NaOH. (Use the lowest possible coefficients. Omit states-­of-­matter in your answer.) OH-­+H+ → H2O OH^-‐‑+H^+ -‐‑-‐‑> H_2O Complete the following table. (Enter your pH values to the 0.1 place.) Green checks and red X's are not displayed for the classification portion of this question. Data Table C: Reaction of HCl and NaOH mL NaOH pH classification 0.0 2.1 acidic 3.0 2.6 acidic 6.0 2.9 acidic 12.0 11.3 basic Acid-­Base Studies 8. 15/15 points | Previous Answers NCSUGenChem102LabV1 1.IL.04. Type your name into the answer box. This space will be used by your instructor to record your points for class participation in the lab using the User Participation Rubric. Steve Yarush Score: 15 out of 15 Comment: -‐‑Responses/last?dep=4450437 8/8 ...
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