phychem

99問 • 1年前

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A sodium ion (Na+) has a mobility µ 5.19×10-8 m2V-1s-1 in an aqueous solution. If an electric field of 10V/m is applied, what is the drift velocity of the ion?

5.19×10-7 m/s

In a moving boundary experiment, why is it necessary to use two ions of significantly different mobilities?

To ensure clear visibility of the boundary

In a solution, the mobility of a cation is 5.0×10-8 m2 V-1 s-1, and the mobility of an anion is 2.0×10-8 m2 V-1 s-1. What is the transport number of the cation (t+)?

0.71

Which property of the solvent plays the most direct role in determining the effect of viscosity on ionic velocity?

The solvent's intermolecular forces

The ionic mobility (u) of ions in an electrolyte:

increases with an increase in temperature due to decreased viscosity and higher thermal energy.

For strong electrolytes at infinite dilution, the molar conductivity (Am-) is given by:

the sum of the individual ionic conductivities of cations and anions.

According to the Debye-Hückel theory, the decrease in ionic velocity at higher ion concentrations is primarily due to:

the development of an ionic atmosphere that opposes the applied electric field.

Which of the following factors does not influence the degree of ionization (a) of an electrolyte in an aqueous solution?

The magnitude of the applied external electric field

In a system where ions are moving in response to an applied electric field, which factor is most directly proportional to the drift velocity of the ions?

The magnitude of the electric field

In a moving boundary experiment, the boundary between two ionic solutions moves 0.5cm in 2seconds under an electric field of 100V/m. What is the apparent velocity of the boundary?

2.5×10-2 m/s

Which of the following factors most significantly affects the transport number of an ion in a solution?

The relative mobilities of cations and anions

The mobility of a sodium ion (Na+) in water at 25-C is 5.19×10-8 m2V-1s-1. If the solvent viscosity doubles, what happens to the mobility of Na+ ?

Halves

For a solution at 298 K, the ionic velocity (v) of a cation is related to the applied electric field (E) and mobility (u) by vuE. If the mobility at 298 K is 5×10-4 m2/V and E-1000V/m, calculate the ionic velocity (v) in m/s.

5×10-2

A solution contains an ion with ionic conductivity 2-3.5mScm2/mol at infinite dilution. Calculate the molar conductivity (Am) for this ion at a concentration of 0.01M. Assume complete dissociation.

35ms cm2/mol

Calculate the ionic strength of a 0.1 M NaCl solution.

0.2mol/L

A 0.01M aqueous solution of acetic acid (CH3COOH) has a molar conductivity (Am) of 40S cm2 mol-1. The limiting molar conductivity (Am) for acetic acid is 3908 cm2 mol-1. Calculate the degree of ionization (a) for acetic acid in this solution.

0.103

Which statement best explains why the specific conductance (K) of a solution decreases upon dilution, while the molar conductance (Am) increases?

Dilution reduces the number of ions per unit volume but increases the mobility of ions, enhancing molar conductance.

How does the conductivity (c) and molar conductivity (Am) of a weak electrolyte behave as the solution is progressively diluted?

K decreases, while Am increases because of higher degree of ionization.

In a conductivity cell, the measured resistance (R) of a 0.0.01M KCl solution is 1002. The cell constant (G*) is 1.0cm-1. Calculate the specific conductivity (k) of the solution.

0.01S cm-1

Which of the following industrial processes relies on measuring the degree of ionization to monitor and control the efficiency of the process?

Manufacturing of high-purity water in the pharmaceutical industry

A 0.01M solution of acetic acid has a molar conductance (Am) of 40S cm2 mol-1. The limiting molar conductance (Am) of acetic acid is 390S cm2 mol-1. Calculate the degree of ionization (a) and determine whether acetic acid is a strong or weak electrolyte.

a=0.103, weak electrolyte

In a conductometric titration of a strong acid (HCl) with a strong base (NaOH), what happens to the conductivity of the solution as NaOH is added beyond the equivalence point?

It increases linearly

The specific conductance (k) of a 0.01M NaCl solution is 1.2×10-3 S cm-1, and its molar conductance (Am) is 1208 cm2 mol-1. If the solution is diluted to 0.001M, the specific conductance becomes 2.0×10-45 cm-1. What is the molar conductance (Am) at the diluted concentration?

300S cm2 mol-1

A 0.01M solution of a weak electrolyte has a conductivity (k) of 1.5×10-4 8 cm-1. Upon dilution to 0.001M, the conductivity decreases to 2.0×10-5 S cm-1. Calculate the ratio of molar conductivity (Am) at 0.001M to that at 0.01M.

6.67

Which of the following is the most appropriate reason why alternating current (AC) is used instead of direct current (DC) in the measurement of electrolytic conductance?

AC minimizes the polarization effect at the electrodes, providing accurate conductance measurements.

In a chemical industry, a solution containing HCl has a conductivity (K) of 0.368 cm-1. If the molar conductivity (Am) of HCI at the same concentration is 360S cm2 mol-1, calculate the concentration of HCI in the solution.

0.01M

Which of the following methods is most suitable for determining whether an electrolyte is strong or weak using conductance measurements?

Compare the molar conductance (Am) at infinite dilution with the limiting molar conductance (Am) for a similar strong electrolyte.

Which of the following titration systems is best suited for a conductometric titration?

Strong acid vs. strong base

During the conductometric titration of HCl with NaOH, the initial conductivity of 50 ml. of 0.1 M HCI is measured as 4.00mS/cm. If the conductivity decreases to 2.00mS/cm after adding 20mL of 0.1 M NaOH, what is the conductivity at equivalence point? Assume water contributes negligible conductivity.

1.00mS/cm

A conductivity meter measures the conductance of a 0.1 m cell filled with a water sample as 250µS. If the specific conductance (k) of the water is determined to be 25µS/cm, what is the concentration of total dissolved solids (TDS) in ppm? Use the empirical relation:

67.00ppm

Why is conductance measurement an effective method for determining the solubility of sparingly soluble salts?

Sparingly soluble salts partially dissociate, and the concentration of ions in solution can be deduced from the conductance.

Which of the following statements correctly explains the behavior of a weak electrolyte in an aqueous solution?

The degree of dissociation of a weak electrolyte increases with dilution, enhancing molar conductivity.

Why is conductance measurement useful in determining the ionic product of water (Kw)?

Conductance provides the combined concentration of H+ and OH- ions, which can be used to calculate Kw.

A pharmaceutical solution has a conductivity (k) of 1.2mS/cm. If the solution contains NaCl as the primary solute, and the molar conductivity of NaCl at this concentration is 1208 cm2/mol, calculate the concentration of NaCl in the solution.

0.01M

A 50 mL. solution of 0.05 M acetic acid (CH3COOH) is titrated conductometrically with 0.1 M NaOH. What is the expected conductivity after adding 25mL of NaOH (half-neutralization point)? (Acetic acid's dissociation constant Ka-1.8×10-5)

1.04mS/cm

Which of the following best describes the relationship between the conductivity of water and its water quality?

High conductivity typically indicates the presence of dissolved salts, which may lower water quality.

The molar conductivity of a saturated solution of BaSO4 is measured as 50µS cm2 mol-1 at 25°C. If the cell constant is 1.0cm-1 and the measured conductivity (k) is 2.5µ8 cm-1, calculate the solubility of BaSO4 in mol/L.

1.25×10-4 mol/L

In a solution of a strong electrolyte such as NaCl, which of the following factors most significantly affects the molar conductivity at high concentrations?

Decrease in ionic mobility due to interionic interactions

The conductivity (K) of pure water at 25°C is measured as 5.5×10-6 S/cm. Given the molar conductivities of H+ and OH- at this temperature are 349.88 cm2/mol and 199.18 cm2/mol, respectively, calculate the ionic product of water (Kw).

1.0×10-14 mol2/1.2

Why are conductance measurements useful in biomedical applications, such as determining the ion concentration in bodily fluids?

Conductance directly correlates to the concentration of all ions present in a solution, providing insights into electrolyte balance.

The molar conductivity (Am) of a 0.01 M solution of a weak acid HA is measured as 8.25 cm2/mol at 25°C. The molar conductivity at infinite dilution (Am) is 390.5S cm2/mol. Calculate the dissociation constant (Ka) of the acid..

1.8×10-4 mol/L

In a galvanic cell, the direction of electron flow is determined by:

The relative reduction potentials of the electrodes.

A galvanic cell is constructed with a silver electrode in 1.0MAgNO3 solution and a zinc electrode in 00.1MZnSO4. The standard reduction potentials are EAg+/Ag +0.80V and EZn2+/Zn = -0.76V. Calculate the EMF of the cell at 25°C using the Nernst equation.

1.56V

The conductivity (k) of a 0.05 M solution of NH4OH is 1.95×10-4S/cm. The molar conductivity at infinite dilution (Am) is 238S cm2/mol. Calculate the dissociation constant (Kb) of NH4OH.

1.8×10-5 mol/L

Which of the following correctly differentiates a concentration cell from a galvanic cell?

A concentration cell generates EMF based on a concentration difference, while a galvanic cell relies on electrode potential differences.

Calculate the standard EMF of a galvanic cell where the cell reaction is: 2Fe3++3Cu→ 2Fe2++3 Cu2+, given EFe3+/Fe2+ = +0.77V and ECu2+/Cu = +0.34V.

0.43V

Why is the Nernst equation critical for understanding electrochemical cell behavior under non-standard conditions?

It accounts for the effect of concentration and temperature on cell potential.

The electromotive force (EMF) of an electrochemical cell is related to the conductance of the electrolyte solution. Which of the following statements is correct regarding this relationship?

EMF increases as the conductance of the electrolyte increases, due to more efficient ion movement.

In the context of battery technology, how is the EMF of a battery related to its efficiency and performance?

The EMF of a battery reflects its ability to do work, but efficiency is determined by the internal resistance.

Which of the following methods can be used to determine the solubility product (Ksp) of a salt using electrochemical principles?

Measuring the electromotive force (EMF) of a saturated solution in a galvanic cell

Which of the following statements best explains the relationship between electrolytic conductance and the EMF in an electrolytic cell?

An increase in the conductance of the electrolyte solution generally decreases the EMF, since less voltage is needed for ion migration.

In a lithium-ion battery, the cell potential (EMF) depends on the lithium ion concentration and the electrode materials. Which of the following changes will result in an increase in the EMF of a lithium-ion battery?

Decreasing the concentration of lithium ions at the cathode.

Which of the following factors primarily contributes to the electrochemical corrosion of metals, as described by the electromotive force (EMF) series?

The relative position of the metal in the EMF series

A galvanic cell is set up using the following half-reactions: Cathode: Cu2+ +2eCu (with E° +0.34V) Anode: Zn Zn2+ +2e- (with E°=-0.76V) If the cell operates under standard conditions, calculate the standard Gibbs free energy change (AG°) for the reaction.

-214.8kJ/mol

The solubility product (Ksp) of a sparingly soluble salt can be determined using the EMF of a cell. What is the primary advantage of using EMF to determine Ksp?

It allows the calculation of Ksp without needing to know the concentration of the ions directly.

A galvanic cell consists of the following half-cells: Zn(s) | Zn (1 M) || Cu²(1 M) | Cu(s). The standard reduction potentials are EZn2+/Zn-0.76V and ECu2+/Cu+0.34V. If the reaction is allowed to proceed, what will be the standard Gibbs free energy (AG°) for the overall reaction?

-211kJ/mol

Which of the following correctly categorizes the material composition of a hydrogen electrode used as a reference in electrochemical measurements?

A platinum electrode in contact with hydrogen gas and a solution of H+ ions

Which of the following statements correctly differentiates the electrodes in a galvanic cell from those in an electrolytic cell?

In a galvanic cell, the cathode is positive, while in an electrolytic cell, the cathode is negative.

Which of the following best describes the working principle of an ion-selective electrode (ISE) used in chemical cells?

It selectively responds to the activity of a specific ion in solution by generating a potential difference.

Which of the following best describes the role of a redox electrode in a chemical cell?

It facilitates a reversible redox reaction involving the transfer of electrons between the electrode and solution.

For the reaction at 25°C: Cu2+ +2e-Cu, the standard electrode potential is ECu2+/Cu+0.34V. If the concentration of Cu2+ is 0.01M and the concentration of Cu is 1.0M, calculate the Gibbs free energy change (AG) for the reaction at these non-standard conditions using the Nernst equation.

-31.0kJ/mol

When considering corrosion as an electrochemical process, which of the following reactions occurs at the anode of the corroding metal in an aqueous environment?

Oxidation of metal to metal ions

For the reaction 2Fe3++Sn2+ 2Fe2++Sn4+, the standard reduction potentials are EFe3+/Fe2++0.77V and ESn4+/Sn2+=+0.15V. What is the equilibrium constant (K) for this reaction at 298K?

4.78×1010

Which of the following is an example of a gas electrode based on material composition?

Platinum electrode in contact with chlorine gas and chloride ions

In the context of a galvanic cell, which of the following best describes the role of the salt bridge?

It maintains electrical neutrality by allowing the migration of ions.

Which of the following statements correctly explains the role of the selective membrane in a fluoride ion-selective electrode?

It facilitates the generation of a potential difference by selectively binding to fluoride ions.

In a chemical cell involving the redox couple Fe3+/Fe2+, which of the following statements correctly identifies the behavior of the redox electrode?

The electrode allows the oxidation of Fe2+ to Fe3+ and the reduction of Fe3+ to Fe2+.

Which of the following statements correctly describes the role of the glass electrode in potentiometric pH measurement?

The glass electrode develops a potential difference across its membrane, which depends on the activity of H+ ions in solution.

Which feature of the glass electrode makes it selectively responsive to hydrogen ions in potentiometric pH measurements?

The exchange of hydrogen ions with alkali metal ions in the hydrated layer of the glass membrane.

Which of the following is the primary requirement for a reference electrode in potentiometric pH measurement?

It must maintain a constant and stable potential under varying solution conditions.

Which of the following design features of combination pH electrodes improves the accuracy and convenience of potentiometric pH measurements?

They integrate the reference and sensing electrodes into a single probe to minimize junction potential errors.

Which of the following statements about Freundlich adsorption isotherm is correct?

It is expressed as x/m=kP1/n (where n>1)

What is the primary function of the reference electrode in a potentiometric pH measurement system?

To provide a stable and known potential against which the glass electrode's potential can be measured.

How does the internal solution in a glass electrode contribute to its function as a hydrogen ion-selective electrode?

It provides a constant internal reference potential for the measurement.

What is the function of the porous junction in a reference electrode used for pH measurements?

To maintain electrical contact with the solution while minimizing contamination of the reference solution

How do gel-filled reference electrodes used in advanced pH electrode designs benefit potentiometric pH measurements?

They eliminate the need for regular refilling of the reference electrolyte.

Langmuir adsorption isotherm is based on which of the following assumptions?

Adsorption is reversible and involves monolayer coverage of the surface.

Which type of adsorption isotherm is characterized by multilayer adsorption at high pressures?

BET isotherm.

Which type of adsorption isotherm is characterized by a plateau that indicates saturation due to monolayer adsorption?

Type 1

Which of the following best describes a Type III adsorption isotherm?

Weak adsorbate-adsorbent interactions.

At low pressure, adsorption generally follows a linear relationship between the amount adsorbed (x/m) and pressure (P). Which isotherm model best describes this behavior?

Henry's law isotherm

Which type of isotherm is associated with a gradual rise in adsorption at low pressures, followed by a steep rise at high pressures due to capillary condensation?

Type IV

For a reaction mechanism involving multiple steps, the step with the highest activation energy is often referred to as:

The rate-determining step

The half-life (11/2) of a first-order reaction is 50 seconds. How long will it take for the reactant concentration to reduce to 1/16 of its initial value?

200 seconds

A second-order reaction with initial concentration [A]0 -0.5mol/L has a rate constant k=0.1L/mol. What will the concentration of [A] be after 10s?

0.250mol/L

The initial concentration of a reactant in a second-order reaction is 0.4mol/L, and the rate constant is 0.1L/mol. After one half-life, the concentration of the reactant is halved. What is the value of the half-life t1/2?

25s

In the context of adsorption isotherms, what does the shape of Type IV isotherm indicate?

Multilayer adsorption followed by capillary condensation in mesopores.

In the IUPAC classification, which type of isotherm is associated with multilayer adsorption on non-porous or macroporous solids without saturation?

Type II

Type IV isotherms are observed for mesoporous materials and show a hysteresis loop. What does this hysteresis loop signify?

Capillary condensation within the pores.

At high pressure, Langmuir adsorption isotherm predicts that:

Adsorption reaches a maximum (plateau) due to monolayer formation.

For the Freundlich isotherm, x/m-kPI/n, at very low pressures (P-0), the amount adsorbed (x/m):

Increases linearly with P.

A reaction has two pathways with activation energies Ea(1) 40kJ/mol and Ea(2) 60kJ/mol. If the pre-exponential factors (A1 and A2) are equal, which pathway is preferred at high temperatures?

Pathway 1 (Ea(1)-40kJ/mol)

The rate constant (k) of a first-order reaction is 00.002s-1. What is the half-life (11/2) of the reaction?

346 seconds

The concentration of reactant A in a second-order reaction is 0.1mol/L at t-0 and 0.05mol/L at t=100s. What is the half-life t1/2 of the reaction?

100s

The rate constant of a third-order reaction is k 0.0212/mol2 s. If the initial concentration of the reactant is [A]0-0.5mol/L, what will be the half-life (11/2) of the reaction?

25s

Which of the following characteristics is not true for a third-order reaction?

The rate of the reaction is proportional to the cube of the concentration of a single reactant.

A reaction follows the Arrhenius equation, and the activation energy Ea is 75kJ/mol. If the rate constant k doubles when the temperature is increased from 298K to 308K, what is the approximate value of the rate constant k at 298K, assuming ko is known to be 5×106s-1?

5×106 s-1

Which of the following best describes the function of a rotating disc electrode (RDE) in specialized chemical cells?

It facilitates mass transport by inducing controlled convection near the electrode surface.

Which of the following is a characteristic feature of a microelectrode in specialized electrochemical applications?

It reduces solution resistance effects due to its small size.

biochem

velante · 99問 · 1年前

biochem