Chemistry Help needed in 1 day

Oct 15th, 2014
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Question description

1.  Consider an aqueous solution that is saturated with nitrogen gas and sugar (glucose) at 80 °C. You may recall from lecture that as for most non-ionic solutes, Ks for glucose increases with increasing temperature.  For N2, as for most gases, KH decreases with increasing temperature.  Predict what happens when:

A.  More sugar is added to the solution at 80 °C.

B.  The solution at 80 °C is heated to 95 °C.

C.  The solution is cooled to room temperature.

2.  Using the Kspdata below, predict the products for the following reaction:

Ca2+(aq) +  NO3-(aq) +  K+(aq) +  F-(aq) -> ???

Ksp Ca(NO3)2 = 1.6 x 10-3 Ksp CaF2 = 3.5 x 10-11

Ksp KNO3 = 1.3 x 106  Ksp KF = 8.7 x 105

3. You are provided with an aqueous solution containing 0.050 M Mg2+ and 0.050 M Cu2+ ions and are asked to try to separate them. What concentration of OH- is needed to begin precipitation of each cation? Ksp = 1.8 x 10-11 for Mg(OH)2; Ksp = 4.8 x 10-20 for Cu(OH)2

4. Calculate how many mL of a 0.1 M NaOH solution was added to a titration mixture of 100 mL of 0.1 M HCOOH (pKa = 3.75) solution to reach a final pH of 5.1.

5. 50 mL of 0.03 M HCl solution was added to 100 mL of 0.10 M acetic acid solution (CH3COOH, Ka = 1.8 x 10-5). What is the pH of the mixture?

6. Consider again the previous problem: What fraction of the acetic acid is dissociated before and after the addition of the HCl solution?

7. Consider a solution of ammonia, NH3. An equal volume of an ammonium chloride solution of the same concentration was added to the ammonia solution. How will this affect the pH of the ammonia solution? Explain your answer.

8. You have 1.0 L of a formic acid buffer that is 0.10 M in HCOOH and 0.050 M in HCOONa. The following substances were added to this buffer in three separate experiments: 1) 0.05 mol of HCl, 2) 0.05 mol of NaOH, 3) 0.05 mol of HCOONa. Which of the resulting solution(s) no longer function(s) as a buffer? Explain your answer.

9. What is the solubility of PbI2(s) in a solution saturated with another sparingly soluble iodide salt relative to PbI2(s) solubility in pure water? Explain your answer.

10. Consider a solution of CaCl2 and Mg(NO3)2 in which the concentrations of both Mg2+ and Ca2+ are the same, 0.01. M.  Is it possible to separate Ca2+ from Mg2+ by selective precipitation of Mg(OH)2? To be precise, is it possible to precipitate 99.99% of magnesium without precipitating any calcium as hydroxides? For the sake of simplicity, assume that the precipitation reactions do not result in any change of the volume of the reaction mixture. The Ksp values of the calcium and magnesium hydroxides are 6.5 x 10-5 and 7.1 x 10-12, respectively. Show your work.

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