Thermochemistry: Solid Sodium Hydroxide
Thermochemistry Lab #2 - Heat of Reaction - Hess's Law Return
The foundation of the study of thermochemistry was laid by the chemist Germain Hess, who investigated heat in chemical reactions during the last century. One statement of the law that bears Hess's name says:
The enthalpy change for any reaction depends on the products and reactants and is independent of the pathway or the number of steps between the reactant and product.
In this experiment, you will measure and compare the quantity of heat involved in three reactions. These heats of reaction will be measured using a styrofoam calorimeter. The three reaction are shown below.
Reaction 1: The dissolving of solid sodium hydroxide in water. NaOH(s) ---> Na+(aq) + OH-(aq) + heat
Reaction 2: The reaction of solid sodium hydroxide with dilute hydrochloric acid. NaOH(s) + H+(aq) + Cl-(aq) ---> Na+(aq) + Cl-(aq) + H2O
Reaction 3: The reaction of sodium hydroxide solution with dilute hydrochloric acid solution. Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) ---> Na+(aq) + Cl-(aq) + H2O Objectives:
To measure and compare the amount of heat involved in three separate but related reactions.
To provide experimental verification of Hess's Law.
Apparatus and Materials:
2 large styrofoam cups
100 mL graduated cylinder sodium hydroxide, NaOH
0.50 M sodium hydroxide solution
0.25 M Hydrochloric acid solution
0.50 M Hydrochloric acid solution thermometers balance
250 mL beaker glass stir stick
Safety:
Hydrochloric acid and sodium hydroxide are corrosive. Avoid direct contact. If any touches your skin, wash it off immediately. Solid sodium hydroxide is especially dangerous because it absorbs moisture rapidly from the air, forming an extremely corrosive liquid. Avoid spilling this solid, and if a spill occurs, clean it up immediately. Be sure to close the lids of bottles of sodium hydroxide securely, immediately after using.
The foundation of the study of thermochemistry was laid by the chemist Germain Hess, who investigated heat in chemical reactions during the last century. One statement of the law that bears Hess's name says:
The enthalpy change for any reaction depends on the products and reactants and is independent of the pathway or the number of steps between the reactant and product.
In this experiment, you will measure and compare the quantity of heat involved in three reactions. These heats of reaction will be measured using a styrofoam calorimeter. The three reaction are shown below.
Reaction 1: The dissolving of solid sodium hydroxide in water. NaOH(s) ---> Na+(aq) + OH-(aq) + heat
Reaction 2: The reaction of solid sodium hydroxide with dilute hydrochloric acid. NaOH(s) + H+(aq) + Cl-(aq) ---> Na+(aq) + Cl-(aq) + H2O
Reaction 3: The reaction of sodium hydroxide solution with dilute hydrochloric acid solution. Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) ---> Na+(aq) + Cl-(aq) + H2O Objectives:
To measure and compare the amount of heat involved in three separate but related reactions.
To provide experimental verification of Hess's Law.
Apparatus and Materials:
2 large styrofoam cups
100 mL graduated cylinder sodium hydroxide, NaOH
0.50 M sodium hydroxide solution
0.25 M Hydrochloric acid solution
0.50 M Hydrochloric acid solution thermometers balance
250 mL beaker glass stir stick
Safety:
Hydrochloric acid and sodium hydroxide are corrosive. Avoid direct contact. If any touches your skin, wash it off immediately. Solid sodium hydroxide is especially dangerous because it absorbs moisture rapidly from the air, forming an extremely corrosive liquid. Avoid spilling this solid, and if a spill occurs, clean it up immediately. Be sure to close the lids of bottles of sodium hydroxide securely, immediately after using.