experiment 1 - answer-basic lab techniques
identification of substances by physical properties
experiment 2 - answer-chromatography
experiment 3 - answer-analysis of hydrated of hydrated salt
experiment 4 - answer-heat of neutralization
sig figs - answer--non zero digits are significan...
GEN CHEM LAB EXAM 1
experiment 1 - answer-basic lab techniques
identification of substances by physical properties
experiment 2 - answer-chromatography
experiment 3 - answer-analysis of hydrated of hydrated salt
experiment 4 - answer-heat of neutralization
sig figs - answer--non zero digits are significant
-any zeros between digits are significant
-zeros to the left of the first non zero digit are not significant
-if a number ends in zeros to the right of the decimal point, those zeros are significant
-If a number ends in zeros to the left of the decimal point, those zeros may or may not
be significant.
-multiplication or division: look at number with least about of sig figs and round there for
new #
-adding or subtracting: line up decimal places and look there
.000 SIG FIGS ON A BALANCE ALWAYS
.05 ON A VOLUME THING
thermochemistry - answer-is the study of energy changes accompanying chemical and
physical reactions.
lab safety basics - answer--wear eye protection
-wear lab coats
-know location of eye wash, showers, fire extinguishers, fire blankets
-say when accident happens
-dont use your mouth to do any suction
-no visitors
-no rowdiness
-no food/water
-wear shoes
-no shorts
-hair up
-no phones
-wash hands
-clean things that get on skin
-clean up spills by telling ta
-clean up things by putting them in the right place under hood
pipetting a liquid or solution - answer--rinse before use
-squeeze bulb above liquid then put into water and release bulb to take up liquid
experiment 1: 2 parts - answer-1. solubility measurements (qualitative)
2. density measurement (quantitative)
solubility measurement in ex1
solid in liquid part - answer--determine solubility of naphthalene in 3 solvents (water,
cytohexane, ethanol)
-add 2/3 crystals of naphthalene into the 3 solvents
-put cork in and shake
solubility measurement results of experiment 1 - answer-cloudiness indicates insolubility
s=soluble
sp=sparingly soluble
i=insoluble
2 layers= immiscibility or lack of solubility in liquid
solubility measurement in ex1
liquid in liquid part - answer-- have the 3 test tubes with (water, cytohexane, ethanol)
with 2 ml in it
- add 4/5 drops of toluene
solubility measurement of unknowns in ex1 - answer-do the same steps of solid in liquid
and liquid in liquid but instead of napthalene use unknown solid and instead of toluene
use unknown liquid
**** always save extra unknowns****
proper use of balance - answer-clean
use brush to make it clean
density measurement ex 1
solid unknown - answer--weigh 1.5 of solid unknown
-use pipet or wash bottles fill 10ml graduated cylinder with solvent in which your
unknown is insoluble
-add solid to liquid in cyclinder (dont loose any solid in transfer process)
-tap sides of cylinder to get solid all the way to the bottom
- read new volume and difference (final-initial) to get volume of solid
-calculate density of solid unknown
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