Chem 15 lab test
Terms
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- what is ohms law
- V=IR
- current measured in:
- amps
- resistance measured in:
- ohms
- squiggle means
- alternating
- two lines, one solid and one dotted means
- direct
- 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
- resistance
- 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
- spontaneous
- an electrolytic cell is
- nonspontaneous, must force current through it
- in electrolytic, anode is:
- positive
- in electrolytic, cathode is:
- negative
- in voltaic, anode is
- negative
- in voltaic, cathode is
- positive
- 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
- base
- purple color means
- acid
- 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