Lab exam 3 Flashcards
Le Chatelier’s Principle
If a chemical reaction is at equilibrium and experiences a change in pressure, temperature, or concentration of products or reactants, the equilibrium shifts in the opposite direction to offset the change.
How can you shift the equilibrium of a reaction?
adding excess reagent, removing product, increasing temperature, increasing concentration
Characteristics of a dehydration reaction
entropy is positive, endothermic, spontaneous at high temperatures
What does a bromine test do and how to interpret the results?
used to support identification of a structure, test for alkene and alkyne unsaturation and in some cases oxidation, aldehydes have positive result, no reaction with aromatics
turning to clear indicates double bond breaking
Orange- negative
Clear- positive
Potassium permanganate test
unsaturation test and not always dependable, produces brown precipitate
purple- negative
dark orange/yellow and brown ppt- positive
What goes into nonhalogenated waste?
acetone rinses, ethanol/ether, solubility tests, organic supernatant, hexanes, ethyl acetate, toulene
What is the rate of a reaction?
concentrations change as a function of time
What is collision theory?
as reactants decrease, reaction rate decreases
How can the rate constant be determined experimentally?
Increasing HCl concentration- can be determined accurately via titration with strong base
What are the factors that influence solvolysis?
concentration of RX, solvent polarity, temperature, substitution of R and identity of leaving group
A carbocation is stabilized by a more?
polar solvent (greater amount of water)
Adding H2O to a solvolysis reaction will do what in comparison to adding iPrOH?
Adding H2O will speed up the reaction, adding iPrOH will slow it down
Characteristics of SN1 reaction
solvent functions as a nucleophile, alkyl halides to a stable carbocation
major limitation: solubility of substrate in solvent
more polar solvent: more rapid ionization
rate is proportional to concentration of haloalkene
rate doubles for every 10 degree temp increase
Br is a better leaving group than Cl
Slower rate is you lower the amount of water and temperature
High water and low temp: exothermic; becomes more endothermic as temp increases
50:50 H2o:iPrOH versus
65:5 H2o: iPrOH
50:50 is endothermic
65:5 is lower energy so exothermic
titration problem about finding concentration of acid
mL NaOH/ 1000 mL * [NaOH]= mol NaOH
mol NaOH= mol acid
mol acid/ L reaction mixture = [acid]
