Reaction order and rate laws #7

Lab Report 7

Reaction Order and Rate Laws

NAME: ____Kimberly Rogers 552/31/7256________

Objectives:

1. To study the effect of reactant concentration on the rate of the
reaction between sodium thiosulfate and hydrochloric acid.

2. To determine the order of each reactant and the rate law for the
reaction.

Background Information:

Define rate of reaction. A measure of how fast a chemical reaction
occurs between reactants.

What are some factors that affect the rate of reaction? The nature of
the reactants, surface area, temperature, catalyst, and concentrations.

How are chemical reaction rates measured? In terms of the time it takes
to complete a reaction or event.

It is measured by the rate of disappearance of reactants and the
appearance of products.

What is a rate law? The relationship between the rate of a chemical
change and the concentration of its reactants. A rate law has the form:
Rate = k[A]n[B]m or A + B ( C



What are the exponents in the rate law? n –and- m are exponents that
reflect how the rate depends on the reactant concentrations. How are
they determined? Experimentally. (cannot be determined merely by
looking at the balanced chemical equation.)



What is the k in the rate law? The rate constant. How is it
determined? Experimentally as well. Depends on temperature not on the
reactants.

How is the overall reaction order determined? The sum of n – plus –
m is the overall reaction order. The exponents n – and – m are
usually positive whole numbers but they may be fractions or may even be
negative numbers.

If the reactant is zero order, how does its concentration affect
reaction rate? The rate is independent of the reactant’s concentration
and that reactant does not appear in the rate law (because anything
raised to the zero power is one.)

If the reactant is first order, how does its concentration affect
reaction rate? The reactant will appear in the rate law and have an
exponent of one (1).

If the reactant is second order, how does its concentration affect
reaction rate? Will appear in the rate law as the concentration of the
reactant squared.

Procedure:

(This is where you should give a brief summary of what you will do.)

Observations/Data:

Data Table 1

Trial Drops

HCl Drops

H2O Drops

Na2S2O3 Initial

HCl Initial

Na2S2O3 Final

HCl Final

Na2S2O3 Time

Tr. 1 Time

Tr. 2 Time

Avg. Rxn

Rate

1 12 0 8 1 0.3







2 6 6 8 0.5 0.3







3 4 8 8 0.33 0.3









Data Table 2

Trial Drops

HCl Drops

H2O Drops

Na2S2O3 Initial

HCl Initial

Na2S2O3 Final

HCl Final

Na2S2O3 Time

Tr. 1 Time

Tr. 2 Time

Avg. Rxn

Rate

1 8 0 12 1 0.3







2 8 6 6 1







3 8 8 4 1









Questions:

Rate law for your reaction:.

Conclusions: