Glossary of Chem 15 lab test

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what is ohms law
current measured in:
resistance measured in:
squiggle means
two lines, one solid and one dotted means
this law is basis for gas thermometer
charles law
charles law says this
volume = constant x temperature
why adding water to bulb extends the range of the thermometer
PV=nRT, less gas in the tube means there is less change in the volume, so the height of the plug varies less, allowing it to move further
advantages of a silicon temp sensor over a Hg in glass thermometer
responds quickly, small and useful in power supplies, environmentally safer, large range, no harmful mercury
alternating voltage setting
V~, 3 4
direct voltage
V line dot dash, 3 4
horseshoe, 3 4
alternating current
A~, 2 4
direct current
A line dot dash, 2 4
numbering of multimeter ports
1 3
2 4
calculate Rf value
Rf=(distance moved by component)/(distance moved by mobile phase front)
mobile phase in paper chromatography
2:1 propanol to water
stationary phase in paper chromatography
piece of chromatography paper
use "like dissolves like" principle to rationalize relative Rf values
sample moves farther because it is the same polarity as mobile phase. something of the opposite polarity does not move very far.
define retention volume Vr
Vr is the volume of the mobile phase required to carry a component through the chromatographic system.
what does a larger Vr mean about a component's ability to interact with the liquid chromatography column?
higher Vr means solutions are less alike and the sample is harder to dissolve
how do you get the best chromatographic seperation?
maximize component migration differences of all components and minimize the component spreading that occurs
stationary phase of gas chromatograph
tide detergent
mobile phase of gas chromatograph
natural gas
why do samples have different retention times?
affinity of gas to the tide, length and tightness of column, gas flow rate
difference between CFC and HCFC?
CFCs have a smaller molar mass, more stable and volatile, cheaper. HCFCs are being phased out because of environmental health problems. carbon halogen bonds do not break down easily causing environmental longevity
practical applications of GC?
science, medicine, and industry; trace pollutants in air, trace drugs in blood, examine petroleum refinery products
a voltaic cell is
an electrolytic cell is
nonspontaneous, must force current through it
in electrolytic, anode is:
in electrolytic, cathode is:
in voltaic, anode is
in voltaic, cathode is
how do you make a lead acid battery?
fill a well with sulfuric acid, connect two pieces of lead to a meter, charge it by connecting it to a 9v battery
what happens when a battery has run down
Ecell at equilibrium goes to Eocell
define chemical kinetics
study of various factors that control the rates of reactions and the study of mechanisms by which reactants become products
what is the rate of reaction determined by?
temperature, concentration, diffusion rate, presence of catalyst
what is the rate determining step
slowest reaction step, determines the rate of the reaction
give definition for mechanism of a reaction
all of the actual elementary steps involving molecules that take place simultaneously or consecutively and that added together give the observed overall reaction
define activation energy
amount of enery required for reaciton to take place
pink color means
purple color means
for an indicator, where do you want the equivalence point?
half way to equivalence point
what effect does a dilution have on pH of a buffer
no effect
what effect does a dilution have on buffer capacity?
capacity decreases
pH = ?
pKa at 1/2 way to equivalence point
henderson hasselbalch
pH=pKa + log Q
Ka =
10 ^ -pKa
why are buffers biologically relevant
buffers keep a system at homeostasis or close to it
what is buffer capacity
abilty to resist small changes in pH

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