CHEM 1C Lecture Notes - Lecture 1: Rate Equation, Reaction Rate Constant, Stoichiometry

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carmineprairie-dog920

25 Jun 2018

School

UC-Irvine

Department

Chemistry

Course

CHEM 1C

Professor

Ramesh D Arasasingham

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➔Reaction rate is the number (mol) of chemical reactions occuring in the system per

reaction volume (L) per time (s)

◆Reaction rate is usually measured in mol/(Lxs)

◆A → B : reaction rate is the number of mol/(Lxs) of A converted into B every

second

◆Rate = -△[A]/△tchange in concentration of A over time period △t

◆Rate = △[B]/△tchange in concentration of B over time period △t

● Because [A] decreases with time, △[A] is negative

➔Average rate: ([A]final - [A]initial) / (tfinal - tinitial)

Example: concentration of O2 decreased from 0.0150 M to 0.0140 M in 3 minutes. Estimate the

average reaction rate

Average rate: –△[O2]/△t= –[O2]final – [O2]initial/ tfinal - tinitial

= –0.0140 M – 0.0150 M180 s

= 5.6 x 10-6 mol/ (Lxs)

➔Reaction rate = moles of reactions per volume (L) per time (s)

◆2 A → B

◆For each mole of the reactions occurred:

● Two moles of A disappeared

● One mole of B was formed

◆To get the reaction rate, the rate of change in [A] and [B] has to be corrected by

the stoichiometric coefficients:

● rate = -(½)( △[A]/△t) rate = △[B]/△t

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Document Summary

Reaction rate is the number (mol) of chemical reactions occuring in the system per reaction volume (l) per time (s) Reaction rate is usually measured in mol/(lxs) A b : reaction rate is the number of mol/(lxs) of a converted into b every second. Rate = - [a]/ t change in concentration of a over time period t. Rate = [b]/ t change in concentration of b over time period t. Because [a] decreases with time, [a] is negative. Average rate: ([a] final - [a] initial ) / (t final - t initial ) Example: concentration of o 2 decreased from 0. 0150 m to 0. 0140 m in 3 minutes. Average rate: [o2]/ t= [o2] final [o2] initial / t final - t initial. Reaction rate = moles of reactions per volume (l) per time (s) For each mole of the reactions occurred:

Related Questions

26. Consider the reaction:
2N2O (g) = 2N2 (g) + O2 (g)
A. Express the rate of the reaction with respect to each of thereactants and products.
B. In the first 15.0 s of the reaction, 0.015 mol of O2 is producedin a reaction vessel with a volume of 0.500 L. What is the averagerate of the reaction over this time interval.
C. Predict the rate of change in the concentration of N2O over thistime interval. In other words, what is [N2O]/t?

Characteristics of second-order reactions

For a second-order reaction, [A]?products, the rate of the reaction is given as rate= k[A]2, where k is the rate constant and [A] is the concentration of reactant A. The integrated rate law for second-order reactions is 1[A]t=kt+1[A]0, where [A]t is the concentration of reactant A at time t, k is the rate constant, and [A]0 is the initial concentration of reactant A. This equation is of the type y=mx+b. Therefore, the plot of 1[A]t versus time is always a straight line with a slope k and a y intercept 1[A]0.

Part B

Consider the second-order reaction:

2NO2(g)?2NO(g)+O2(g)

Use the simulation to find the initial concentration [NO2]0 and the rate constant k for the reaction. What will be the concentration of NO2 after t = 40.0s ([NO2]t) for a reaction starting under the condition in the simulation?

Express your answer in moles per liters to three significant figures.

26. Consider the reaction: 2N20(8) ► 2 N2(8) + O2(8) a. Express the rate of the reaction in terms of the change in concentration of each of the reactants and products. b. In the first 15.0 s of the reaction, 0.015 mol of O2 is produced in a reaction vessel with a volume of 0.500 L. What is the average rate of the reaction during this time interval? c. Predict the rate of change in the concentration of N O dur. ing this time interval. In other words, what is A[N20/At?

CHEM 1C Lecture Notes - Lecture 1: Rate Equation, Reaction Rate Constant, Stoichiometry

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