Calculate molar solubility of ZnCO₃ in a buffer solution of pH = 7

A 1.0-L buffer solution contains 0.100 molHC2H3O2 and 0.100 molNaC2H3O2. The value of Ka for HC2H3O2 is 1.8×10−5 Calculate the pH of the solution upon addition of 39.8 mL of 1.00 MHCl to the original buffer.

(19) Ammonium formate, NH4(HCOO), dissolves in water to give ammonium ions and formate ions. These ions then undergo an unfavorable and endothermic Brønsted acid- base reaction according to this equation:

NH4+ (aq) + HCOO– (aq) NH3 (aq) + HCOOH (aq)

Keq < 1 (at 298 K)

∆H_orxn > 0

(a) (8 pts.) Calculate Keq and ∆G_orxn (at 298 K) for equation (19).

(b) (6 pts.) Qualitatively, would one expect ∆S_orxn for equation (19) to be positive or negative? Briefly justify your answer.

(c) (10 pts.) If 1.00 mol NH4(HCOO) is dissolved in 1.00 L water at 298 K, what is the pH of the solution?

(d) (7 pts.) The solution from part (c) (1.00 mol NH4(HCOO) in 1.00 L water) can be made into an effective buffer at pH = 3.00 by the addition of either NaOH or HCl. Specify whether NaOH or HCl would be required, and whether more than 0.500 or less than 0.500 mol of the reagent would be needed.

(e) (8 pts.) Consider the solution from part (c) (1.00 mol NH4(HCOO) in 1.00 L water at 298 K). For each of the changes below, circle the effect on the concentration of NH3 (aq) at equilibrium after the change is made, and briefly give the reasoning for your choice.

NH4+ (aq) + HCOO– (aq) NH3 (aq) + HCOOH (aq)

Keq < 1 (at 298 K)

∆H_orxn > 0
(i) The temperature of the solution is increased to 340 K.

[NH3] increases [NH3] decreases [NH3] does not change

Explanation:

(ii) The volume of the solution is increased to 2.00 L by adding 1.00 L water.

[NH3] increases [NH3] decreases [NH3] does not change

Explanation:

The common laboratory solvent ethanol is often used to purify substances dissolved in it. The vapor pressure of ethanol, CH3CH2OH, is 54.68 mm Hg at 25 °C. In a laboratory experiment, students synthesized a new compound and found that when 30.10 grams of the compound was dissolved in 269.1 grams of ethanol, the vapor pressure of the solution was 53.72 mm Hg. The compound was also found to be nonvolatile and a non-electrolyte. What is the molecular weight of this compound? ethanol = CH3CH2OH = 46.07 g/mol. what is the molar weight?

The average molecular weight of the triglycerides in coconut oil is 680 g/mol. How much NaOH (in grams) is required to completely saponify this oil? Why is it important to use less than this amount when preparing soap?

Pyridine is used in the synthesis of tosyl chloride from tosic acid, and also in reactions that involve tosylate esters. What characteristic of pyridine makes it the base of choice for these reactions? What might happen if a base were used that did not have this particular characteristic?

How does soap remove an oil spot?

The very useful restriction enzyme SpoBob hydrolyses the phosphodiester bond between the guanylates in the sequence AGGACCA. Is SpoBob generating blunt or sticky ends? Please explain.

this is actually biochemistry

The concentration of NO3– in a water sample is determined by a onepoint standard addition using a NO3– ion-selective electrode. A 25.00-mL sample is placed in a beaker and a potential of 0.102 V is measured. A 1.00-mL aliquot of a 200.0-mg/L standard solution of NO3– is added, after which the potential is 0.089 V. Report the mg NO3–/L in thewater sample.

Briefly describe how you would determine whether a given salt will produce an acidic, basic, or

neutral solution when dissolved in water.

Synthesis of potassium trioxalatoferrate (volumetric techniques and KMnO4 titration)

Work the following problems:

a. suppose you have as much 0.03200 M KMnO4 as you need. State exactly what data must be recorded in order to analyze a solid of potassium trioxalatoferrate for both iron and oxalate.

b. Describe the titration endpoint:

c. State the critetion for reading a buret filled with KMnO4:

d. A solution is 0.020 M in KMnO4. A student asked to prepare 500.0 mL of Na2C2O4 solution, 25.00 mL aliquots of which will be used to standardize the KMnO4. If approximately 33 mL of KMnO4 are to be used in each titration, describe exactly how you would prepare the sodium oxalate solution. Show all calculations.

(M.W.: Na2C2O4= 134.0)

Talking about Chromatography using kool aid, 70% isopropanol, 25% isopropanol and 5% isopropanol what is the answer to the questions?

1. Describe h0w you think the separation is occurring. What is the mechanism of the separation?

2. Why do you think the consistency of the solution added to the column was changed throughout the separation? This process is called gradient elution.

3. All chromatography systems consist of a mobile phase and a stationary phase. Define the system: what is/are the stationary phase(s), mobile phase(s), sample(s), analyte(s)?

4. Rank each colored component from least polar to most polar. Justify your ranking based on the order of elution.

Use chemfinder to find the chemical structures of the dyes. Draw the structures and justify your ranking based on their structures.

5. Many analytical procedures require a separation (chromatography) step prior to the analysis. Why?

6. This lab is a “qualitative” lab. It could easily be modified to be a “quantitative” lab. Briefly describe how you could make this a quantitative lab, i.e., how could you determine the concentration of the dyes in the Kool-Aid sample?

7. Compounds need not be colored to be analyzed using chromatography. How could colorless compounds be detected in a chromatography system?

How could you dissociate a diatomic molecule, at equilibrium, without changing the temperature of the system? [Suggested key words: equilibrium constant, concentration, ratio, volume...]

This is a P-Chem problem

The haf reaction occuring in the standard hydrogen electrode "SHE" is
2H⁺ (aq) +2e- <=> H₂ (g)

a) What is the EMF for this half-cell?
b) How is the EMF value listed in part (a) above for the standard ydrogen electrode measured?
c) Why do we need a "standard reference electrode" like this hydrogen half-cell?
d) How is SHE used to determine unknown half-cell voltages?