Ch.14 - Chemical Kinetics

Problem 20c

Chapter 14, Problem 20c

A flask is charged with 0.100 mol of A and allowed to react to form B according to the hypothetical gas-phase reaction A1g2¡B1g2. The following data are collected: Time (s) 0 40 80 120 160 Moles of A 0.100 0.067 0.045 0.030 0.020 (c) Which of the following would be needed to calculate the rate in units of concentration per time: (i) the pressure of the gas at each time, (ii) the volume of the reaction flask, (iii) the temperature, or (iv) the molecular weight of A?

Verified step by step guidance

Step 1: Identify the given data and the reaction: A(g) -> B(g). The table provides the moles of A at different times.

Step 2: To calculate the rate of reaction in units of concentration per time, we need to convert moles of A to concentration. This requires the volume of the reaction flask (ii).

Step 3: Use the formula for concentration: [A] = moles of A / volume of the flask.

Step 4: Calculate the change in concentration of A over time intervals to determine the rate of reaction. Rate = -Δ[A]/Δt.

Step 5: The pressure of the gas at each time (i), the temperature (iii), and the molecular weight of A (iv) are not needed to calculate the rate in units of concentration per time.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reaction Rate

The reaction rate is a measure of how quickly reactants are converted into products in a chemical reaction. It is typically expressed in terms of concentration change over time, such as moles per liter per second (mol/L/s). Understanding how to calculate the rate requires knowledge of the initial and final concentrations of reactants or products at specific time intervals.

Concentration

Concentration refers to the amount of a substance (solute) present in a given volume of solution or mixture. In gas-phase reactions, concentration can be expressed in terms of moles per volume (e.g., mol/L). To calculate the concentration of a gas, one must know the number of moles and the volume of the container, which is essential for determining the reaction rate.

Ideal Gas Law

The Ideal Gas Law (PV = nRT) relates the pressure (P), volume (V), temperature (T), and number of moles (n) of a gas. This law is crucial for understanding how changes in these variables affect gas behavior. In the context of the question, knowing the pressure and volume of the gas is necessary to convert moles of A into concentration, which is required to calculate the reaction rate.

Recommended video:

Guided course

01:15

Ideal Gas Law Formula

Related Practice

Textbook Question

Consider the following hypothetical aqueous reaction: A(aq) → B(aq). A flask is charged with 0.065 mol of A in a total volume of 100.0 mL. The following data are collected: Time (min) 0 10 20 30 40 Moles of A 0.065 0.051 0.042 0.036 0.031 (a) Calculate the number of moles of B at each time in the table, assuming that there are no molecules of B at time zero and that A cleanly converts to B with no intermediates.

views

Textbook Question

Consider the following hypothetical aqueous reaction: A(aq) → B(aq). A flask is charged with 0.065 mol of A in a total volume of 100.0 mL. The following data are collected: Time (min) 0 10 20 30 40 Moles of A 0.065 0.051 0.042 0.036 0.031 (b) Calculate the average rate of disappearance of A for each 10-min interval in units of M>s.

Textbook Question

Consider the following hypothetical aqueous reaction: A(aq) → B(aq). A flask is charged with 0.065 mol of A in a total volume of 100.0 mL. The following data are collected: Time (min) 0 10 20 30 40 Moles of A 0.065 0.051 0.042 0.036 0.031 (c) Between t = 10 min and t = 30 min, what is the average rate of appearance of B in units of M/s? Assume that the volume of the solution is constant.

Textbook Question

The isomerization of methyl isonitrile (CH₃NC) to acetonitrile (CH₃CN) was studied in the gas phase at 215°C, and the following data were obtained:

Time (s) [CH₃NC] (M)

0 0.0165

2000 0.0110

5000 0.00591

8000 0.00314

12,000 0.00137

15,000 0.00074

(a) Calculate the average rate of reaction, in M/s, for the time interval between each measurement. (c) Which is greater, the average rate between t = 2000 and t = 12,000 s, or between t = 8000 and t = 15,000 s?

Textbook Question

The isomerization of methyl isonitrile (CH₃NC) to acetonitrile (CH₃CN) was studied in the gas phase at 215°C, and the following data were obtained:

Time (s) [CH₃NC] (M)

0 0.0165

2000 0.0110

5000 0.00591

8000 0.00314

12,000 0.00137

15,000 0.00074

(b) Calculate the average rate of reaction over the entire time of the data from t = 0 to t = 15,000 s.

Textbook Question

The isomerization of methyl isonitrile (CH₃NC) to acetonitrile (CH₃CN) was studied in the gas phase at 215°C, and the following data were obtained:

Time (s) [CH₃NC] (M)

0 0.0165

2000 0.0110

5000 0.00591

8000 0.00314

12,000 0.00137

15,000 0.00074

(d) Graph [CH₃NC] versus time and determine the instantaneous rates in M/s at t = 5000 s and t = 8000 s.

views