Phosphorus pentachloride decomposes according to the chemical equation.

A 0.457 mol sample of PCl5(g) is injected into an empty 4.85 L reaction vessel held at 250

For the diprotic weak acid H2A, Ka1 = 2.6

Calculate the pH for each of the following cases in the titration of 50.0 mL of 0.160 M HClO(aq) with 0.160 M KOH(aq). The ionization constant for HClO is 4.0×10^-8.
(a) before addition of any KOH
pH=
(b) after addition of 25.0 mL of KOH
pH=
(c) after addition of 40.0 mL of KOH
pH=
(d) after addition of 50.0 mL of KOH
pH=
(e) after addition of 60.0 mL of KOH
pH=

One of the main functions of saliva is to buffer against acid from food and plaque, which contributes significantly to the formation of cavities. While there are several buffers in saliva, carbonic acid (H2CO3) has the highest concentration and has the greatest effect on pH.

(a) While the salivary concentration of carbonic acid stays at a fairly constant 1.3 mM, the level of bicarbonate (HCO3-) can vary with the rate that saliva flows from salivary glands. For low flow rates, the bicarbonate concentration is around 2 mM; for medium flow rates, it is 30 mM; and for high flow rates, around 60 mM. The pKa of carbonic acid at body temperature is 6.1. Assuming that the pH of Saliva is determined primarily by carbonic acid and bicarbonate, determine the pH of saliva for each of the three flow rates. The normal pH of saliva is about 6.3.

(b) The most prevalent bacterium in the mouth, streptococcus mutans, breaks down sugar and releases lactic acid (pKa = 3.86). If S. mutans has produced 10^-8 moles of lactic acid since your last swallow, what is the pH of your saliva? What would the pH be without the bicarbonate buffer? Assume that your mouth contains about 1 mL of saliva and that your saliva is flowing at a low rate.

(c) You take a drink of orange juice, and after you swallow, 0.5 mL remains in your mouth. What is the pH of your saliva if your mouth contains 1 mL of pure saliva, and if you model orange juice as 1.0 mM citric acid (pKa = 3.13; assume only one dissociation).

(d) Why do some toothpastes contain baking soda (sodium bicarbonate)?

Could you use saturated sodium bicarbonate as a test reagent to distinguish between the following pairs of compounds

1. Aspirin and ibuprofen

2. Aspirin and methyl salicylate

Explain you rationale clearly, describing what you might expect to observe when each substance is mixed with the test reagent

2. Liquid ammonia (boiling point = -33.14

The amount of I3–(aq) in a solution can be determined by titration with a solution containing a known concentration of S2O32–(aq) (thiosulfate ion). The determination is based on the net ionic equation

2S₂O₃^2-(aq) + I₃^- (aq)---------> S₄O₆^2-(aq) + 3I^-(aq)

Given that it requires 40.1 mL of 0.340 M Na2S2O3(aq) to titrate a 15.0-mL sample of I3–(aq), calculate the molarity of I3–(aq) in the solution.

The double acetylation of the drug morphine gives a historically important compound. Discuss.

Suppose you want to make at most 10 cups of trail mix, using all of the ingredients. You dont want either ingredient to dominate the mixture so you want each ingredient to contribute at least 10% of the total volume of the mix made. You want the entire amount of trail mix to have no more than 7000 calories and you want to maximize the the amount of carbohydrates in the mix. (Use "solver" or an equivalent program because the simplex method gets to complicated)

1) What constraints must be placed on the objective function?

2) Find the number of cups of each ingredient in the mix so the amount of carbohydrates is maximized.

3) How many grams of carbohydrates are in a cup of the final mix? How many calories?

4) Under all the constraints given about, what recipe for the trail mix will maximize the amount of protein in the mix? How many grams of protein are in a cup of the mix? Calories?

5) Consider making a batch of trail mix under the following conditions: You still want to make at most 10 cups of trail mix, and you still want each of the ingredients to contribute at least 10% of the total volume of the mix made. You want the entire amount of trail mix you make to have at least 1000 grams of carboyhydrates, and you want to minimize the amount of fat in the mix. What recipe for trial mix will minimize the amount of fat in the mix?

6) How much fat, protein and carbohydrates are in a cup of this mix?

7) How many calories are in a cup of this mix?

An aqueous solution of magnesium oxalate is prepared by dissolving 4.46 g of magnesium oxalate in 1.51×10² g of water. The density of the solution is 1.01 g mL^-1.

a) Determine the mass percent of magnesium oxalate in the solution.

b) Determine the mole fraction of magnesium oxalate in the solution.

An aqueous solution of nickel(II) chloride is prepared by dissolving 5.61 g of nickel(II) chloride in 4.53×10² g of water. The density of the solution is 1.34 g mL^-1.


Determine the molarity (in mol/L) of nickel(II) chloride in the solution.

I saw a talk today and they mentioned how nitrogen-vacancy diamond centers can be used to optically induce spin polarization and now I wonder what other ways there are to induce a spin polarization.

Thank you!

a) Explain how a sodium ion (Na+ 1) is created, its stability and why it takes on this charge. List the following values to help you answer this question: the size of the sodium ion; atomic size of the neutral atom and the Effective nuclear charge; each ionizations potential for each electron in the atom; the electron affinity and the electronegativity. Reference your source for this information.

b) Explain atomic size, ionization potential, electronegativity and the general periodic trend for each of these properties. Arrange the following atoms: O, Se, C, Si, F in order of increasing atomic radius, in order of increasing electronegativity and in order of increasing ionization energy. Explain how you developed your list and explain the similarities or differences between the lists.

The Beer’s Law calibration curve for this experiment was obtained at the appropriate wavelength and gave the following linear regression equation:
Absorbance = 4898 (Concentration) + 0.055

Suppose 5.0 mL of 0.0020 M Fe(NO₃)₃ dissolved in 0.50 M HNO₃ are mixed with 5.0 mL of 0.0020 M HSCN dissolved in 0.50 M HNO₃, and the absorbance of the solution is measured to be 0.30. What is the equilibrium constant for the following reaction? Assume that the H⁺ concentration stays constant at 0.50 M.

Fe³⁺(aq) + HSCN(aq) ⇌ FeSCN²⁺(aq) + H⁺(aq)

Complete combustion of 3.60 g of a hydrocarbon produced 11.6 g of CO2 and 3.95 g of H2O. What is the empirical formula for the hydrocarbon?

Based on the information given, classify each of the pure substances as elements or compounds, or indicate that no such classification is possible because of insufficient information.

Analysis with an elaborate instrument indicates that •Substance A contains two elements. •Substance B and Substance C react to give a new Substance D. •Substance E decomposes upon heating to give Substance F and Substance G. •heating Substance H to 1000°C causes no change. •Substance I cannot be broken down into simpler substances by chemical means. •Substance J cannot be broken down into simpler substances by physical means. •heating Substance K to 500°C causes it to change from a solid to a liquid.