## An experimenter places the following concentrations of gases in a

An experimenter places the following concentrations of gases in a closed container: [NOBr] = 7.13 × 102 M, [NO] = 1.58 × 102 M, [Br2] = 1.29 × 102 M. These gases then react:

2NOBr(g) ⇌ 2NO(g) + Br2(g)

At the temperature of the reaction, the equilibrium constant Kc is 3.07 × 104. Calculate the reaction quotient, Qc, from the initial concentrations and determine whether the concentration of NOBr increases or decreases as the reaction approaches equilibrium.

a. Qc = 6.33 × 104; the concentration of NOBr decreases

b. Qc = 6.33 × 104; the concentration of NOBr increases

c. Qc = 1.58 × 104; the concentration of NOBr increases

d. Qc = 4.65 × 104; the concentration of NOBr decreases

e. Qc = 4.65 × 104; the concentration of NOBr increases

## You are running the reaction 2A + B → C

You are running the reaction 2A + B → C + 3D. Your lab partner has conducted the first two experiments to determine the rate law for the reaction by the method of initial rates.

Presuming that you can measure the initial rate of each experiment, which of the following concentrations for Experiment 3 would help you to determine the rate law easily?

a. [A] = 0.0330 M, [B] = 0.0330 M
b. [A] = 0.0125 M, [B] = 0.0500 M
c. [A] = 0.0250 M, [B] = 0.0400 M
d. [A] = 0.0250 M, [B] = 0.0330 M
e. [A] = 0.0500 M, [B] = 0.0330 M

## Potassium superoxide,KO2, is often used in oxygen masks (such as

Potassium superoxide,KO2, is often used in oxygen masks (such as those used by firefighters) because KO2 reacts with CO2 to release molecular oxygen. Experiments indicate that 2 mol of KO2 (s) react with each mole of CO2(g).

(a) The products of the reaction are K2CO3(s) and O2(g).Write a balanced equation for the reaction between KO2(s) and CO2(g).

(b) Indicate the oxidation number for each atom involved in the reaction in part (a). What elements are being oxidized and reduced?

(c)What mass of KO2(s) is needed to consume 18.0 g CO2(g)? What mass of O2(g) is produced during this reaction?

## Suppose the Ka values for the hypothetical acids HX, HY,

Suppose the Ka values for the hypothetical acids HX, HY, and HZ are 9.5 × 105, 7.6 × 104, and 1.2 × 102, respectively. Assuming that “A” is a cation that produces a slightly soluble salt with all three acids, which of the following salts

would have its solubility most affected (compared with its solubility

in pure water) when it is dissolved in a 0.10 M solution

of HCl?

a. AX

b. AY

c. AZ

d. The solubility of all the salts would be affected by the same amount.

e. There is not enough information given in the problem to determine the answer.

## Neutron activation analysis is an analytical technique in which a

Neutron activation analysis is an analytical technique in which a sample of material is bombarded with neutrons from a fission reactor. When a 35.0-g aluminum can is irradiated, it has an initial activity of 40.0 curies (Ci). The safety office won’t let you touch anything having an activity in excess of 0.100 Ci. Assuming all the radioactivity is from 28Al, which has an halflife of 2.28 min, how many minutes do you have to wait after bombardment before you can handle the can safely?

a. 17.0 min

b. 1.32 × 103 min

c. 19.7 min

d. 478 min

e. 476 min

## Which of the following statements best explains why nitrogen gas

Which of the following statements best explains why nitrogen gas at STP is less dense than Xe gas at STP?

(a) Because Xe is a noble gas, there is less tendency for the Xe atoms to repel one another, so they pack more densely in the gas state.

(b) Xe atoms have a higher mass than N2 molecules. Because both gases at STP have the same number of molecules per unit volume, the Xe gas must be denser.

(c) The Xe atoms are larger than N2 molecules and thus take up a larger fraction of the space occupied by the gas.

(d) Because the Xe atoms are much more massive than the N2 molecules, they move more slowly and thus exert less upward force on the gas container and make the gas appear denser.

## Furoic acid (HC5H3O3) has a Ka value of 6.76 ×

Furoic acid (HC5H3O3) has a Ka value of 6.76 × 10-4 at 25 °C. Calculate the pH at 25 °C of

(a) A solution formed by adding 25.0 g of furoic acid and 30.0 g of sodium furoate (NaC5H3O3) to enough water to form 0.250 L of solution;

(b) A solution formed by mixing 30.0 mL of 0.250 M HC5H3O3 and 20.0 mL of 0.22 M NaC5H3O3 and diluting the total volume to 125 mL;

(c) A solution prepared by adding 50.0 mL of 1.65 M NaOH solution to 0.500 L of 0.0850 M HC5H3O3.

## Two buffers are prepared by adding an equal number of

Two buffers are prepared by adding an equal number of moles of formic acid (HCOOH) and sodium formate (HCOONa) to enough water to make 1.00 L of solution. Buffer A is prepared using 1.00 mol each of formic acid and sodium formate. Buffer B is prepared by using 0.010 mol of each.

(a) Calculate the pH of each buffer, and explain why they are equal.

(b) Which buffer will have the greater buffer capacity? Explain.

(c) Calculate the change in pH for each buffer upon the addition of 1.0 mL of 1.00 M HCl.

(d) Calculate the change in pH for each buffer upon the addition of 10 mL of 1.00 M HCl.

(e) Discuss your answers for parts (c) and (d) in light of your response to part (b).

## The solubility of CaCO3 is pH dependent.a) Calculate the molar

The solubility of CaCO3 is pH dependent.

a) Calculate the molar solubility of CaCO3 (Ksp = 4.5 × 10-9) neglecting the acid–base character of the carbonate ion.

(b) Use the expression for the CO32- ion to determine the equilibrium constant for the reaction

(c) If we assume that the only sources of Ca2+, HCO3, and ions are from the dissolution of CaCO3, what is the molar solubility of CaCO3 using the preceding expression? What is the pH?

(d) If the pH is buffered at 8.2 (as is historically typical for the ocean), what is the molar solubility of CaCO3?

(e) If the pH is buffered at 7.5, what is the molar solubility of CaCO3? How much does this drop in pH increase solubility?

## Oxyhemoglobin, with an O2 bound to iron, is a low-spin

Oxyhemoglobin, with an O2 bound to iron, is a low-spin Fe(II) complex; deoxyhemoglobin, without the O2 molecule, is a high-spin complex.

(a) Assuming that the coordination environment about the metal is octahedral, how many unpaired electrons are centered on the metal ion in each case?

(b)What ligand is coordinated to the iron in place of O2 in deoxyhemoglobin?

(c) Explain in a general way why the two forms of hemoglobin have different colors (hemoglobin is red, whereas deoxyhemoglobin has a bluish cast).

(d) A 15-minute exposure to air containing 400 ppm of CO causes about 10% of the hemoglobin in the blood to be converted into the carbon monoxide complex, called carboxyhemoglobin. What does this suggest about the relative equilibrium constants for binding of carbon monoxide and O2 to hemoglobin?

(e) CO is a strong-field ligand. What color might you expect carboxyhemoglobin to be?