University College - Chemistry Chem 112A Lecture Notes - Lecture 9: Ph

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limehorse889

8 Feb 2017

School

WUSTL

Department

University College - Chemistry

Course

University College - Chemistry Chem 112A

Professor

D' Arcy

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Document Summary

0. 1 x e x 0. 1 + x. Ka = x(0. 1 + x)/(0. 1-x) = 1. 76 x 10-5 = [h3o+][oac-]/[hoac] ph = -log(x) = 4. 75, so solution is acidic. In this case ka > kb, if the opposite had been true, then the solution would be basic. Disturb a system at equilibrium by adding an acid or base, then determine the new ph. [h3o+] = # mol/v = 0. 1 m *0. 1 l /1. 1l = 9. 1 x 10-3 m. [oac-] = [hoac] = 0. 1m * 1l/1. 1l = 9. 1 x 10-2 m. I: 9. 1 x 10-2 9. 1 x 10-3 9. 1 x 10-2. Ka = 1. 76 x 10-5 = x(0. 0819 + x)/(0. 1001 x) X = [h3o+] = 2. 15 x 10-5 ph = 4. 67. Note that solution has not changed that much, despite the addition of hcl. Same system, but with the addition of a base: [oh-] = 100ml . 1 m naoh/1. 1l = 9. 1 x 10-3 m.

Related Questions

Textbook is showing HCl + NaOH titrating problem. After adding 5 mL of NaOH, why is the equation OH + H3O _--> 2h2o? Where is the h3o coming from

1. Determine the amount of solute in the following samples:

500 ml of 0.2 M KI (potassium iodide)

220 ml of 0.03 M H2SO4 (sulfuric acid)

2.5 l of 0.1 M MgNO3 (magnesium nitrate)

1 ml of 5 M HCl (hydrochloric acid)

This problem requires that you know what molarity (M) is. M (molarity) = # of moles of solutes / Liter of solution. You are given the volume. You should be able to obtain moles of solutes. Your answers can be in moles or grams (either one will be acceptable).

2. How many ml of 0.1 M HCl would be required to titrate 35 ml of 1 M NaOH to the end point?

This is an acid/base reaction.

1) First, write out the balanced chemical reaction for HCl + NaOH.

2) Second, figure out the number of moles of NaOH in 35 ml of 1 M NaOH.

3) How many moles of HCl is required for completely reacting with the moles of NaOH in Part 2).

3. What is the pH of a 0.03 M solution of the strong base NaOH?

1) This question requires that you know pH = - log [H₃O⁺], or simply as pH = - log [H⁺] (to make it easier).

2)So, you have to know how to use your scientific calculator to do log function (check Youtube).

3) This question also requires that you know: pOH = - log [OH^-].

4) This question also requires that you know: [H₃O⁺][OH^-] = 1.0 x 10^-14 or pH + pOH = 14

5) First step, determine the concentration of OH^- in 0.03M NaOH when it dissociates or breaks up into Na⁺ and OH^-.

6) This will give you [OH^-]. You can plug this into pOH = - log [OH^-] to get pOH.

7) Once you get pOH, then use (pH + pOH = 14) to get pH.

4. Balance the chemical reactions shown below and then write equilibrium expressions for each. All reactants and all products are in the gas phase.

CO + F₂ ------> COF₂

CH₄ + O₂ ------> CO₂ + H₂O

N₂O₄ -----> Br₂ + NO

BrNO -----> Br₂ + NO

1)This problem requires that you know how to balance chemical equations.

2)After you balance the equation, you need to know the equilibrium expression

5. Determine the oxidation states of each element comprising the following ionic compounds:

KClO₄

NaMnO₄

Sr(NO₃)₂

NaHCO₃

CH₄

In this question you are going to calculate the data that could be used to construct a titration curve (pH versus volume of titrant added) for the titration of an aqueous ammonia (NH3; weak base, pKB = 4.7) cleaning solution with a strong acid (HCl). When strong acid is added to an aqueous solution, it immediately reacts and yields H3O + ions; thus the titration is described by the reaction: NH3(aq) + H3O + (aq) ïï NH4 + + H2O(l) K = 2.0x109

The cleaning solution is produced by adding 0.02 moles of NH3 to 1.0 L of pure H2O, which you later titrate with 1.0 M HCl titrant solution. To simplify matters weâll assume all activity coefficients = 1.0 for all species in this problem. Utilize the ICE (INITIAL, CHANGE, EQUILIBRIUM)Table Method (show your work) to determine the pH of the system when various amounts of the strong acid (titrant) have been added. Note: when you solve the quadratic function, make sure to select the root that is positive, and if you have two positive roots, use the root that represents a realistic change; i.e. the change isnât greater than what was physically added to the system or greater than the concentration of reactant it reacts with.

a. Calculate pH of solution when 0 mL of titrant have been added (only the NH3 has been added)

a1. Calculate pH of solution when 10 mL of titrant have been added

University College - Chemistry Chem 112A Lecture Notes - Lecture 9: Ph

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