Chem Lab exam 2

1. Analyte: The chemical species being analyzed in the solution

2.  Aliquot: A measured sub-volume of a sample

3. Titrant: A solution of known concentration that is added to a sample during a titration

4.  Equivalence point: A point at which the amount of titrant added is exactly enough to completely react with the analyte in the solution

5. Endpoint: is the point at which the indicator changes color, signaling that the titration is complete.

6.  blanking the instrument: involves setting the spectrophotometer to zero absorbance using a blank solution

7. Beer-Lambert Law: The Beer-Lambert Law, also known as Beer's Law. The law is expressed by the equation: A=e*c*l

8. Blank: is a sample that contains all the components of the test solution except the analyte

9. Y-value: -value represents the value on the vertical axis.

10. Stoichiometry: is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction.

11.  Ligand: a molecule or ion that binds to a central metal atom or ion to form a coordination complex.

12.  coordination complex: also known as a coordination compound, consists of a central metal atom or ion bonded to surrounding molecules or ions called ligands

13. complex ion: is a charged species consisting of a central metal ion bonded to one or more molecules or ions called ligands.

14. Lamda max: is the wavelength at which a substance absorbs the maximum amount of light.

Know how to identify:

Enthalpy of a Reaction: 

• Do you understand how the reactions were set up and carried out? (use of a calorimeter, preparation of a buret, recording buret readings to correct significant figures, massing solid reagents, how to properly transfer reagents, how to properly use a balance)

• Do you know why a calorimeter was used to measure heat evolved by an exothermic reaction?

• Can you determine the moles of a limiting reagent given molarity and volume used?  Given mass and molar mass?

• Do you know how to use Hess's Law to predict the enthalpy of a reaction given experimental data? 

  pH Meter Titration:

  • Know basics of the pH meter titration setup: importance of calibrating the pH meter, proper positioning of the electrode in a stirring solution, delivering sodium hydroxide, recording data. 

  • Can you explain how to prepare a pipet for use and record its volume to the correct number of significant figures?

  • Can you determine the volume of sodium hydroxide needed to reach the equivalence point given a titration curve?

  • Can you calculate the molarity of nitric acid given titration data?

    
    Acid Base Titration: 

    • Review the titration setup: titrant in the buret, analyte and indicator in an Erlenmeyer flask, use of a magnetic stir plate.

    • Do you know the difference between an endpoint and equivalence point in a titration?

    • Can you calculate the average volume of titrant needed to reach an endpoint given data from multiple trials? 

      Spectrophotometry: 

      • Review how to use a buret: delivering specific quantities of solution from a buret, recording readings to the correct significant figures.

      • Review new vocabulary: coordination complex, complex ions, ligand ect. (there are a lot of new words).

      • Can you explain the relationship between the concentration of a solution and its absorbance as related to the Beer-Lambert Law?

      • Can you determine the necessary volume of ligand needed to reach the stoichiometric point from a plot created during this experiment, absorbance versus mL ligand? 

      KNOW bold words in the Procedure Overview and Data Analysis section.