Chemistry Rate of Reaction Quiz

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Questions and Answers

What does the instantaneous rate of consumption of a reactant represent?

The total amount of reactant consumed

The change in concentration of the product over time

The total change in mass during a reaction

The change in concentration of a reactant over time (correct)

In the reaction A + 2B → 3C + D, how is the rate of formation of product D expressed?

Equal to the rate of consumption of A

Half the rate of consumption of A

Twice the rate of consumption of B

One-third the rate of formation of C (correct)

If the rate of formation of 2NO is 0.16 mmol dm-3 s-1, what is the rate of consumption of NOBr?

0.64 mmol dm-3 s-1

0.16 mmol dm-3 s-1 (correct)

0.08 mmol dm-3 s-1

0.32 mmol dm-3 s-1

What is the rate of formation of CH3CH3 if the rate of change of CH3 radicals is -1.2 mol dm-3 s-1?

0.60 mol dm-3 s-1 Signup and view all the answers

What is the general form of a rate law for a reaction?

Rate = k[A]^a[B]^b Signup and view all the answers

In the ionic form of the reaction Mg(s) + 2HCl(aq) → H2(g) + MgCl2(aq), what type of ion is Cl- considered?

Spectator ion Signup and view all the answers

Which of the following statements regarding stoichiometry is true for A + 2B → 3C + D?

The rate of consumption of B is twice the rate of formation of D. Signup and view all the answers

Which term describes the rate at which the concentration of a reactant decreases over time?

Rate of reaction Signup and view all the answers

What represents the order of reaction with respect to a species in a rate law?

The exponent to which the concentration of the species is raised Signup and view all the answers

What is the overall order of a reaction with the rate law $v = k[A]^{1/2}[B]$?

3/2 Signup and view all the answers

What does a zero-order rate law imply about the reaction rate?

The rate is constant regardless of the concentration of reactants Signup and view all the answers

In the pseudo first-order rate law, what is approximated as constant?

The concentration of one reactant in large excess Signup and view all the answers

If a reaction has the rate law $v = k[A]^{m}[B]^{n}$, how are m and n characterized?

They can vary independently of the concentrations Signup and view all the answers

What does the rate constant (k) depend on?

The temperature and nature of the reaction Signup and view all the answers

What is true about individual reaction orders in a rate law?

They can be fractional or zero Signup and view all the answers

What is the significance of determining a rate law experimentally?

It reveals the mechanism of the reaction Signup and view all the answers

What does the method of initial rates measure?

The rate of reaction at the beginning with different reactant concentrations. Signup and view all the answers

What does the slope of the plot of log vo against log [I]o indicate?

The order of reaction with respect to I. Signup and view all the answers

If the order of reaction with respect to Ar is one, how does this affect the rate law?

It makes the reaction first-order in Ar, contributing to the overall reaction order. Signup and view all the answers

What is the initial rate law derived from the given slopes in the problem?

vo = k[I]o2 [Ar]o Signup and view all the answers

What does the intercept of the plot of log vo against log [I]o represent?

The logarithm of the rate constant k. Signup and view all the answers

How are the orders of reaction determined for both I and Ar?

By plotting logarithms of rates against concentrations and assessing slopes. Signup and view all the answers

If the concentration of I doubles, how does the rate change if the order is two?

The rate increases by four times. Signup and view all the answers

What type of function is expected when plotting log vo against log [A]o?

A straight line. Signup and view all the answers

Study Notes

Rate of Reaction

The rate of reaction is the change in concentration of a reactant or product over time.
The rate of consumption of a reactant is a positive quantity.
The rate of formation of a product is also a positive quantity.
The stoichiometry of the reaction dictates the relationship between the rates of consumption and formation of different reactants and products.
- For example, in the reaction A + 2B → 3C + D, the rate of formation of C is three times the rate of consumption of A.
The rate of reaction can be expressed in terms of molar concentration, molecules per cubic centimeter, or other appropriate units.

Rate Laws and Rate Constants

The rate law is an equation that describes the rate of a reaction as a function of the concentrations of the reactants.
The rate constant is a proportionality constant in the rate law that reflects the intrinsic rate of the reaction.
The rate law is determined experimentally and cannot be predicted from the stoichiometry of the reaction.
The reaction order with respect to a particular reactant is the exponent to which its concentration is raised in the rate law.
The overall order of a reaction is the sum of the individual orders with respect to each reactant.

Determining the Rate Law

Isolation Method: This method involves keeping the concentrations of all reactants except one constant, allowing for the determination of the order of reaction with respect to the isolated reactant.
- The rate law can then be approximated by the pseudo-first-order rate law.
Method of Initial Rates: This method involves measuring the initial rate of reaction for different initial concentrations of reactants.
By analyzing the relationship between initial rates and initial concentrations, the reaction orders and the rate constant can be determined.

Example: Recombination of Iodine Atoms

The reaction of iodine atoms in the presence of argon is an example of a reaction whose rate law can be determined using the method of initial rates.
The results of the experiment show that the reaction is second-order with respect to iodine atoms and first-order with respect to argon atoms.
The rate constant for the reaction was determined to be 9 x 10^9 mol^-2 dm^3 s^-1.

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Description

Test your understanding of the rate of chemical reactions and the factors influencing them. This quiz covers topics such as reaction rates, stoichiometry, rate laws, and rate constants. Dive deep into the mechanics of how concentration changes over time affect reactions!