Entalphy of solutions part2
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This document discusses the enthalpy of neutralization reaction between acids and bases. It states that the enthalpy of neutralization is the energy released per mole of water formed in an acid-base reaction, which is an exothermic property. When a strong acid reacts with a strong base, water and heat are produced in an exothermic reaction. The experiments described involve measuring the temperature change when hydrochloric acid and nitric acid each react separately with sodium hydroxide to determine the enthalpy change.
Entalphy of solutions part2
- 3. ENTHALPY (HEAT) OF NEUTRALIZATION OF AN ACID-BASE REACTION By : Dr. Robert D. Craig, Ph.D. Enthalpy of neutralization: energy released per mole of water formed in an acid-base reaction – an “exothermic” property
- 4. ENTHALPY (HEAT) OF NEUTRALIZATION OF AN ACID-BASE REACTION Enthalpy of neutralization: energy released per mole of water formed in an acid-base reaction –an “exothermic” property The negative sign is a result of the heat which is lost by the system to the surroundings The reaction of a strong acid with a strong base is a exothermic reaction that produces water and heat as products
- 5. These acids are dangerous
- 6. ENTHALPY (HEAT) OF NEUTRALIZATION OF AN ACID-BASE REACTION H3O+ (aq) + OH- (aq) 2 H2O (l) + heat
- 7. Secondary caution as well • Acid to the Water! • Why add the acid to the water? Because the same general concept described above applies when you're mixing an acid or a base to water. A base is the opposite of an acid and they are corrosive for different reasons
- 8. ENTHALPY (HEAT) OF NEUTRALIZATION OF AN ACID-BASE REACTION Enthalpy change, Hn = -specific heat (H20) x combined massed (Acid - Base) x DT (H20)
- 9. This will be done for two acids Page 296 see data sheet HCl + NaOH HNO3 + NaOH
- 10. Acid base pair number one • HCl + NaOH Clean two 250 mL Erlenmeyer flasks with soap, then rinse and drain. Repeat this until they drain cleanly without leaving droplets adhering to the sides, using purified water for a final rinse.
- 11. pair number one • Clean and dry the calorimeter with a towel. Make sure it doesn't leak. From the solutions available in the laboratory, rinse one of the Erlenmeyer flasks with a few mL of 0.500 M HCl and then drain. Rinse the other flask with a few mL of 0.500 M NaOH and drain. Label the flasks to avoid confusion
- 12. Becareful!!!!!!!50x • To obtain an accurate temperature measurement, it is essential that the thermometer bulb be completely emersed in the solution. If reaching thermal equilibration takes a long time, you may wish to dry off the thermometer and recheck the acid temperature before the final mix
- 13. Be careful!!!! 50x • If the two temperatures differ a bit before mixing, take the initial mixed solution temperature to be the average of the acid and base temperatures. Finally, carefully pour the base into the acid, stir gently with the thermometer, and record the exact time of mixing.
- 14. Acid base pair number two • HNO3 + NaOH • Please redo the same procedure as you did for • HCl + NaOH •
- 15. Last sentence • Enthalpy change, Hn is generally expressed in units of kJ/mol of water that forms from the reaction. • The mass (grams) of the solution equal the combined masses of the acid and base solution (this is important!!!!)