Stoichiometry Flashcards
STP
T = 273 K
22.4 L/mol
What happens when not all organic vapor fully displaces air from flask when heat removed?
The flask would not be 100% organic vapor -> decreased yield
What happens to compounds in combustion analysis?
Compounds oxidized and oxide gas collected
ex. CO2, SO2
Why can’t the mass percent of oxygen in a compound be determined directly using combustion/elemental analysis
- when the carbohydrate is oxidized, the oxygen can be found in both water and carbon dioxide
- procedure involves adding excess oxygen so the oxygen from carbohydrate and oxygen reactant cannot be distinguished
- oxygen is already fully reduced in carbohydrate and does not react with oxygen gas to be oxidized
Two solutes with the same mass percent, which one has highest molarity?
The solute with the lowest molecular weight would have the greater number of moles.
Why is water rinsed through a pipet after it transfers solution?
To ensure complete transfer of the solution. In addition, the rinsing is not quantitative and doesn’t measure volume, the flask with the solution measures volume.
What is a ten-fold dilution?
A ten-fold dilution is defined as a dilution that results in a final concentration of a solution
that is ten percent of its original concentration. Final volume should be ten times initial volume.
How to make the greatest dilution?
The greatest dilution results from the greatest relative addition of solvent.
Adding solvent to a solution dilutes the solution and decreases?
Decreases molarity, molality, percent solution
NOT density, it depends on relative density of the solvent and solution, so density can increase or decrease
Increasing density of solution does what to molarity and molality?
Increases both molarity and molality because greater concentration of solute
Wavelength of colors?
700nm = red 400nm = purple
Negative value for change in entropy means….
Gain in order, losing randomness so the number of molecules probably decrease too
