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CHEMEX4
Kinetics and nuclear
Question | Answer |
---|---|
The rate of reaction must be... | positive (thats why need negative sign in front of equation) |
In RXn, the reactant concentration.... | decreases with time because reactants are consumed |
In RXn, the product concentration... | increases with time because products are formed. |
average rate of rxn _______ as progresses | decreases |
For most reactions, the rate depends on the... | concentrations of the reactants |
what is n in the rate law equation? | the reaction order |
if n = 0, ..... | reaction order is zero; rate is independent of the concentration of A |
if n= 1,.... | reaction order is first order; rate directly proportional to concentration of A |
if n=2, ..... | reaction is second order; rate is proportional to the square of the concentration of A |
Zero order reaction: concentration of reactant... | decreases linearly with time; the rate is constant because the reaction does not slow down as the concentration of A decreases. |
First order reaction: concentration of reactant... | is directly proportional to the rate of reaction; rate slows down as reaction proceeds because the concentration of reactant decreases. |
Second order reaction, the rate of reaction is.. | proportional to the square of the concentration of the reactant; the rate is even more sensitive to reactant concentration and slope of curve flattens out more quickly than in first-order |
DETERMINING THE ORDER OF A REACTION | the order of a reaction can be determined only by experiment. A common way to determine reaction order is by the method of initial rates. |
initial rate- | the rate for a short period of time at the beginning of the reaction |
in a first order reaction, the value of the rate consta,t k, can be determined by | solving the rate law for k and substituting the concentration and initial rate from any of the one of three measurements |
For a zero-order reaction, the initial rate is | the same at all measured initial concentrations |
for a second-order reaction, the initial rate ... | quadruples for a doubling of the reactant concentration |
the integrated rate law for a chemical reaction is a relationship between | concentrations of reactants and time |
the half life of a reaction(t 1/2) | time required for the concentration of the reactant to fall to one-half of its initial value |
half life of first order reaction: | t 1/2= 0.693/ k; so, k = 0.693/ (t 1/2) |
shorter half life= | larger k |
collision theory: how will increasing concentration affect the rate of chemical reaction? | increase rate of rxn, increase # of colisions between reactant molecules |
collision theory: how will increasing the temperature affect the rate of chemical reaction? | increease rate of rxn, increase frequency of collisions, increase kinetic energy w/ which they collide, resulting in greaterfraction of collsions producing product |
collision theory: how will addition of a catalyst affect the rate of chemical reaction? | increase rate of rxn, alters rxn pathway, lower activation enerygy for new reaction pathway |
Advantages of nuclear power | 1) no CO2 produced 2) not dependent on foreign oil 3) a lot of energy from small amount of fuel |
Disadvantages of nuclear power | 1) waste is radioactive for a long time 2) accidents can release radioactivity 3) fuel could be diverted for weapons |
what is a PET scan work? | uses radiation, or nuclear medicine imaging, to produce 3-dimensional, color images of the functional processes within the human body. PET stands for positron emission tomography. |
how does a pet scan work? | The machine detects pairs of gamma rays which are emitted indirectly by a tracer (positron-emitting radionuclide) which is placed in the body on a biologically active molecule. The images are reconstructed by computer analysis |
A PET scan uses __________________ that naturally emit ____________________ which interact with __________________ | radioactive isotope; positrons; a nearby negatively charged electron |
why is radon hazardous? | it decays to 218 Po which is a solid and alpha emitter. If radon decays while in the lungs, it leaves a solid alpha-emitter behind which will continue to emit radiation |
when 131/53I undergoes beta decay, it becomes.. | 131/54 Xe |
with beta decay, bottom number.. | increases by 1 |
with alpha decay.. | top number 4 less, bottom number 2 less |