# The quantitative relationship of a reaction at equilibrium lab

Once equilibrium is established, the reaction is over, right? Not exactly. An experimenter has some ability to affect the equilibrium. Chemical equilibria can be. reaction reaches equilibrium when the concentrations of the reactants and Quantitatively, the relative amounts of the two reactants and the product are this experiment is to calculate the formation constant, which leaves us in a bit of a .. Use the data in Table 2 to explain, in words in a general sense, the relationship. The Heat of Reaction is the change in the enthalpy of a chemical reaction. In endothermic reactions, (\(ΔH>0\)) heat is.

For example, the equilibrium between the slightly soluble salt gypsum, CaSO4. Experimental Procedure Required Reagents: The Shifting of an Equilibrium.

### Le Chatelier's Principle - Chemical equilibrium

The Common Ion Effect. Mix this, and observe any change. Now add several drops of 6 M NaOH with mixing, until a change occurs. Interpret the observed changes in terms of "shifting the equilibrium. Explain your observations in terms of the equilibrium equation and the "common ion" effect.

Le Chatelier's Principle Equlibrium Concentration, Temperature, Pressure, Volume, pH, & Solubility

To each of two 3 mL samples of 0. To one sample add 1 M NH4Cl, a few drops at a time, with mixing. To the other add 6 M HCl, a drop at a time, with mixing. In each case, note any changes in colour and in odour of the solutions. Write the equation for the equilibrium in dilute NH4OH and interpret the different observed results, including the additional overall net ionic equation for the reaction with HCl, in terms of shifting the equilibrium.

Verify this as 5. Write an equation for the ionic equilibria present in a saturated NaCl solution. Explain your observations in terms of the equilibrium equations involved.

To a 5 mL portion of this, add a little 0. Fe OH 3 is quite insoluble. Do your data prove the correctness of the above equation? Form the data obtained we can calculate an equilibrium constant according to the equation. You can assume essentially complete reaction, so that the concentration of the red complex can be calculated as equal to the total SCN- concentration in the mixture. We can measure this decreased concentration by removing solution from the first known standard sample until the colours, viewed lengthwise through the tubes, exactly match.

The concentrations will then be inversely proportional to the respective depths of solution. Solution Preparation Select five clean cm test tubes of the same diameter, and label them 1 to 5. Thus, one can look at this situation as an increase in the effective concentration of the dissolved ions due to less solvent available and, likewise, causes precipitation of NaCl. Once again, from the experiment you performed before this one, you were told that the concentration of a saturated NaNO3 solution is about 7.

The saturated NaCl is about 5.

### Equilibrium Lab #2

Since the concentrated solution of NaNO3 is devoid of Cl- ions, its addition actually reduces [Cl-] since, remember, we are also adding water in the process.

The [Cl-] is essentially reduced to half of its original value, it is now 2. Contrast this to the result when one adds concentrated HCl, the previous experiment.

Change in reactant or product concentration If a chemical system is at equilibrium and we add a substance either a reactant or a productthe reaction will shift so as to reestablish equilibrium by consuming part of the added substance. Conversely, removal of a substance will result in the reaction moving in the direction that forms more of the substance.

Remember that this is a change in concentration so changing the amount of a pure solid or liquid which is already in equilibrium should not make the reaction consume the additional solid or liquid. Example, if solid NaCl is already in equilibrium with a saturated solution of NaCl, adding more pure NaCl solid will not cause additional dissolving.

Conversely, removal of some of the solid NaCl which is in equilibrium with a saturated solution of NaCl will not cause further crystallization of NaCl from the saturated solution. Effects of volume and pressure changes These effects are present when the two opposing reactions are of different molecularity. In solution, volume changes can be achieved by addition of solvent. Changing the volume effectively changes concentration. Adding more solvent is essentially a dilution. If the number of solute species on the reactant side is not the same as on the product side, then volume changes can cause a shift in equilibrium.

Increasing the volume favors the process with lower molecularity. Increasing the volume then will cause the system to shift in the direction that increases the number of solute species. This is the same for reactions involving gases. Decreasing the volume of the container causes an equilibrium mixture of gases to shift in the direction that reduces the number of moles of gas.

For gases, increasing the pressure by adding one of the gases participating in the reaction, will also disturb equilibrium This is essentially a change in reactant or product concentration.

## Effect of Temperature on Equilibrium

Increasing the total pressure of a reaction vessel by adding a spectator gas does not affect equilibrium. Remember that volume changes can only have effect if the number of solute species or gas species in the reactant side is not equal to the if the number of solute species or gas species in the product side.

Effect of Temperature One can treat heat as a reactant for an endothermic process or a product for an exothermic process and the same principle used for changes in concentration of reactants or products can be used to deduce the effect of heat on an equilibrium reaction.