Physical chemistryLesson 1 of 3 in the course Kinetics

Measuring, Interpreting, and Comparing Chemical Reaction Rates

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

Save course
Lesson progress
0 / 5

Your progress is kept in this browser only.Sign up to save it

Summary

A reaction rate describes how quickly a chemical reaction consumes reactants or forms products. This lesson introduces ways to measure reaction progress and shows how changes in concentration over time can be written as a rate expression.

A rate measures how a property changes over time. Familiar examples include the distance traveled per unit time (speed) and money earned per unit time (wage). A reaction rate similarly measures how much reactant is consumed or product is produced in a given time.

All flashcards

What does a chemical reaction rate measure?
The change in the amount or concentration of a reactant consumed or product formed per unit time.
How is the instantaneous rate of a disappearing reactant read from a concentration–time graph?
It is the negative of the tangent-line slope at the chosen time.
What is the initial rate of a reaction?
The instantaneous rate at time zero.
Why are species rates divided by their stoichiometric coefficients?
To express each species' concentration-change rate as the same normalized reaction rate.
Why must a glucose test strip be read at its recommended time?
Reading too early can miss color development; reading too late can allow interfering reactions to produce color.

Quiz questions

  1. On a concentration-versus-time graph, the tangent to a reactant's curve at a particular time has slope −0.020 mol L−1s−1-0.020\ \text{mol L}^{-1}\text{s}^{-1}. What is the reactant's instantaneous rate of consumption?Answer: 0.020 mol L−1s−10.020\ \text{mol L}^{-1}\text{s}^{-1}
  2. For 2H2O2→2H2O+O22H_2O_2 \rightarrow 2H_2O + O_2, hydrogen peroxide is consumed at 3.20×10−2 mol L−1h−13.20\times10^{-2}\ \text{mol L}^{-1}\text{h}^{-1}. At what rate does oxygen form?Answer: 1.60×10−2 mol L−1h−11.60\times10^{-2}\ \text{mol L}^{-1}\text{h}^{-1}
  3. For 2NH3→N2+3H22NH_3 \rightarrow N_2 + 3H_2, ammonia is consumed at 2.10×10−6 mol L−1s−12.10\times10^{-6}\ \text{mol L}^{-1}\text{s}^{-1}. What is the nitrogen formation rate?Answer: 1.05×10−6 mol L−1s−11.05\times10^{-6}\ \text{mol L}^{-1}\text{s}^{-1}
  4. A typical glucose test strip is read at about 30 seconds. What may happen if it is read too soon?Answer: Insufficient color may have formed, producing a false negative.
  5. For the reaction aA→bBaA \rightarrow bB, which expression gives the normalized reaction rate?Answer: −1aΔ[A]Δt=1bΔ[B]Δt-\frac{1}{a}\frac{\Delta[A]}{\Delta t}=\frac{1}{b}\frac{\Delta[B]}{\Delta t}

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

More in Physical chemistry

All Physical chemistry lessons
Physical chemistryReaction-Rate Factors: Reactants, Surface Area, and Conditions5 flashcards · 5 quiz questions · 4 gamesPlay free →Physical chemistryChemical Kinetics: Rate Laws, Experimental Methods, and Applications5 flashcards · 5 quiz questions · 4 gamesPlay free →Physical chemistryPrimary and Rechargeable Batteries and Hydrogen Fuel Cells5 flashcards · 5 quiz questions · 4 gamesPlay free →Physical chemistryElectrolysis: Cell Reactions, Aqueous Products, Electroplating, and Faraday Calculations5 flashcards · 5 quiz questions · 4 gamesPlay free →Physical chemistryIntegrated Rate Laws, Diagnostic Plots, and Half-Lives by Reaction Order5 flashcards · 5 quiz questions · 4 gamesPlay free →Physical chemistryNuclear Magnetic Resonance: Spin, Spectroscopy, Relaxation, and Applications5 flashcards · 5 quiz questions · 4 gamesPlay free →