Illustrated Guide to Home Chemistry Experiments

Chapter 13 Laboratory: Chemical Equilibrium and Le Chatelier’s Principle 231

LABORATORY 1 3.1:

oBSERvE LE CHATELIER’S pRINCIpLE IN ACTIoN

Le Chatelier’s Principle states that a forced

change in concentration, temperature, volume,

or pressure results in change to the dynamic

equilibrium state. In this lab, we’ll examine

various reactions that are in a state of dynamic

chemical equilibrium, force changes to each

of these environmental characteristics, and

observe the results.

RIREEqU d EqUIpmENT ANd SUppLIES

£ goggles, gloves, and protective clothing

£ dropper or Beral pipette (3)

£ test tubes (6) and rack

£ beaker, 150 mL (2)

£ alcohol lamp or other heat source

£ ring stand

£ support ring

£ wire gauze

£ stirring rod

£ tap water

£ sodium chloride (~40 g)

£ sodium carbonate (~1.6 g)

£ magnesium sulfate (~1.3 g)

£ hydrochloric acid, concentrated (~5 mL)

£ small bottle of carbonated soft drink (2, one chilled

and one at room temperature)

CUTIOA nS

With the exception of concentrated hydrochloric acid,

the chemicals used in this laboratory are reasonably

safe. Hydrochloric acid is toxic, corrosive, and produces

irritating fumes. This experiment uses an open flame,

so use caution and have a fire extinguisher handy. Wear

splash goggles, gloves, and protective clothing.

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SBSTITUTIU oNS ANd modIfICATIoNS

• You may substitute ordinary table salt for the sodium
  chloride.


• You may substitute washing soda or soda ash for the
  sodium carbonate.


• You may substitute Epsom salts for the magnesium
  sulfate.


• You may substitute muriatic acid (from the hardware
  store) of 30% or higher concentration for the
  hydrochloric acid.

dISoALp S : All of the solutions used in this laboratory

can safely be flushed down the drain with copious water.

This lab has four parts, each of which examines one of the effects
of concentration, temperature, volume, and pressure on dynamic
equilibrium states. As you observe each experiment, record
your observations in the Observations section that follows the
procedure sections.

POCEDURER

PART I: ExNEAmI THE EffECT of
CoNCENTRATIoN oN EqUILIBRIUm
In this part of the lab, we examine the effect of changing the
concentration of the reactant ions on a saturated solution of
sodium chloride (NaCl). That solution contains sodium ions (Na+)
and chloride ions (Cl–). To saturated sodium chloride solution
samples, we’ll add concentrated hydrochloric acid (which
contains Cl– ions but not Na+ ions), saturated sodium carbonate
solution (which contains Na+ ions but not Cl– ions), and saturated
magnesium sulfate solution (which contains neither), and
observe the effects on the saturated sodium chloride solution.

1. If you have not already done so, put on your splash
   goggles, gloves, and protective clothing.


2. Prepare a saturated solution of sodium carbonate by
   adding about 1.6 g of sodium carbonate to 5 mL of water
   in a test tube. Stir or shake the solution to ensure that the
   sodium carbonate dissolves completely, and continue