Pyridine is a weak base that is used in the manufacture of pesticides and plastic resins. It is also a component of cigarette smoke. Pyridine ionizes in water as follows:

C5H5N+H2O⇌C5H5NH++OH−

a) The pKb of pyridine is 8.75. What is the pH of a 0.440 M solution of pyridine?

Benzoic acid is a weak acid that has antimicrobial properties. Its sodium salt, sodium benzoate, is a preservative found in foods, medications, and personal hygiene products. Benzoic acid dissociates in water:

C6H5COOH⇌C6H5COO−+H+

b) The pKa of this reaction is 4.2. In a 0.63 M solution of benzoic acid, what percentage of the molecules are ionized?

Chemical Weapon ​Phosgene, COCl₂, gained notoriety as a chemical weapon in World War I. Phosgene is produced by the reaction of carbon monoxide with chlorine:

CO(g) + Cl₂(g) <=> COCl₂(g)

           The value of K_c for this reaction is 5.0 at 600 K. What are the equilibrium partial pressures of the three gases if a reaction vessel initially contains a mixture of the reactants in which P_CO = P_Cl2 = 0.265 atm and P_COCl2 = 0.000 atm?

Average K_eq: 235.8

Does your data support a complete conversion or partial conversion? Based on your results was the measured K_eq too high or too low? Explain please.

A solution of household bleach contains 5.25% sodium hypochlorite, NaOCl, by mass. Assuming that the density of bleach is the same as water, calculate the volume (in mL) of household bleach that should be diluted with water to make 500.0 mL of a pH = 10.18 solution.

Sodium sulfate is slowly added to a solution containing 0.0500 M Ca2 (aq) and 0.0350 M Ag (aq). What will be the concentration of Ca2 (aq) when Ag2SO4(s) begins to precipitate? Solubility-product constants, Ksp, can be found here.

1. Calculate [Ca^2+] = _____M

2. What percentage of the Ca2+ (aq) can be precipitated from the Ag+ (aq) by selective precipitation? ______%

The first-order rate constant for the decomposition of N2O5,

2N2O5(g)→4NO2(g)+O2(g)

at 70∘C is 6.82×10−3 s−1. Suppose we start with 2.80×10⁻² mol of N2O5(g) in a volume of 2.2 L .

How many moles of N2O5 will remain after 6.0 min ?

How many minutes will it take for the quantity of N2O5 to drop to 1.6×10⁻² mol ?

What is the half-life of N2O5 at 70∘C?

Part A

How many moles of HF (Ka=6.8×10−4) must be added to water to form 0.230 L of solution with a pH of 2.50?

Express your answer using two significant figures.

n=____mol

Carbon disulfide is prepared by heating sulfur and charcoal. The chemical equation is

S2 (g) + C (s) <----> CS2 (g)     Kc=9.40 at 900K

How many grams of CS2(g) can be prepared by heating 12.4 moles of S2(g) with excess carbon in a 7.20 L reaction vessel held at 900 K until equilibrium is attained?

#15.114

Calculate the concentration of all species in a 0.165 M solution of H2CO3. (express to 2 sig figs)

[H2CO3], [HCO−3], [CO2−3], [H3O+], [OH−]

#15.80 Find the pH of each of the following solutions of mixtures of acids. (express answers to 2 decimal places)

1) 8.0×10⁻² M in HNO3 and 0.180 M in HC7H5O2

2) 9.0×10⁻² M in HF and 0.220 M in HC6H5O

3) 0.110 M in formic acid and 5.5×10⁻² M in hypochlorous acid

Part A) Find the pressure in mmHg of a 0.124 g sample of helium gas in a 649 mL container at 34 ∘C. Express the pressure to three significant figures and include the appropriate units.

Part B) xture with a total pressure of 770 mmHg contains each of the following gases at the indicated partial pressures: 140 mmHg CO2, 112 mmHg Ar, and 128 mmHg O2. The mixture also contains helium gas.

What is the partial pressure of the helium gas?

What mass of helium gas is present in a 23.0-L sample of this mixture at 263 K ?

Part C)  cylinder with a moveable piston contains 0.76 mol of gas and has a volume of 337 mL .

What is its volume after an additional 0.26 mol of gas is added to the cylinder? (Assume constant temperature and pressure.)

Express your answer to three significant figures.

Part D) A gas mixture with a total pressure of 770 mmHg contains each of the following gases at the indicated partial pressures: 140 mmHg CO2, 112 mmHg Ar, and 128 mmHg O2. The mixture also contains helium gas.

What mass of helium gas is present in a 23.0-L sample of this mixture at 263 K ?

Express your answer in grams.

One hundred moles of CO at 300ºC is burned with 100 moles of O2 which is at 100ºC; the exit gases leave at 400ºC. What is the heat transfer to or from the system in kJ? Define whether the heat is transferred to or away from the system.

Mole fraction and mass percent:

1) An aqueous solution is36.0 % by masspotassium bromide,KBr, and has a density of 1.33 g/mL.

The mole fraction ofpotassium bromide in the solution is .

2) The mole fraction ofammonium carbonate,(NH₄)₂CO₃, in an aqueous solution is6.61×10^-2 .

The percent by mass ofammonium carbonate in the solution is  %.

Listed below are the constants in three activity-coefficient equations: Wilson's, Margules' and van Laar's, for the system ethanol-water. In addition, the vapor-liquid equilibria at one pressure are tabulated.

a) Using the Wilson equation and the constants listed below, find the bubble pressure and vapor composition for a mixture of 30 mol% ethanol at 90 C

b) Using the Wilson equation, find the dew pressure and composition for a mixture of 80 mol% ethanol at 110 C

c) Using the Wilson equation, find the bubble temperature and composition for a mixture of 20% ethanol at 3.0 bar

d) Using the Wilson equation, find the dew temperature and composition for a mixture of 40% ethanol at 3.0 bar

Data:

Antoine Constants