Chem 161 Chapter 16

What variable is put over time to determine reaction rates

change in concentration of reactants

The higher ________ of reactants, the greater the reaction rate due to increased __________.

concentration; collisions

The ________________ of the reactants influences reaction rate because substances must ____ in order for particles to collide

physical state; mix

The ______ the temperature, the greater the reaction rate due to higher _____ for collisions

greater, energy

A hot steel nail glows when placed in O2. However, when the same mass of steel wool is placed in the same container, it bursts into flames. why?

because the steel wool has more surface area, allowing for more collisions to occur and have an explosive reaction rate.

What is the formula for expressing reaction rate of a homogenous mixture? (reactants or products)

[change in conc of A] / [change in time]

How should the reaction rate equation for a reactant differ from a product and why?

Reactants should have a neg on the outside because they’re always decreasing but the rate is always a pos.

what is the general form for reaction rates

aA+bB=cC+dD (reactants will have neg)

Write the more applicable form of reaction rates

rate= -1/a (change in A)/change in time = -1/b(change in B)/change in time = 1/c(change in C)/change in time=1/d(change in D)/change in time

Why is the rate law important?

It tells the mechanisms of the reactions and allows rate to be calculated at a single point with only concentration

what is the formula for rate law?

Rate= K[A]^m[B]^n

rate constant

K; specific for a given temperature and doesn’t change as reaction proceeds

Reaction order

m and n; determined by experimentation, define how the rate is affected by reactant concentrations

first order example

reaction doubles when A doubles

second order example

reaction quadruples when A doubles

zero order example

reaction remains the same when A doubles

What happens when you double the concentration of NO in k[NO]²[O2]? write the new rate law.

The reaction rate quadruples. k[2NO]²[O2]

How do you determine the reaction rate?

a series of experiments in which one reaction is kept constant while the other is changes. Then you measure the effect on the reaction rate in each case.

how do you calculate rate constant?

plug in reaction rates and A and B concentration then solve for K