, what is __. [10 points]Nuclear chem. & kinetics test [85 points] Honors chemistry
For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer.
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Signature: ___________________
1. Write the nuclear equation for __ / fill-in the blank. [15 points]
a. alpha decay of tin - 120: ____________________________
b. positron emission of phosphorus – 32: _________________________
c. 235 U --> 2 neutrons + barium – 140 + _______.
2. The half-life of 3 H is 12.5 years. A radioactive sample currently has 5.0 mCi of 3 H (Ci = 3.7 * 1010 isotopes disintegrate / second) and originally contained 25 mCi of 3 H. What is the age of the sample ? [10 points
3. What does the equation, E = m c2 , mean ? [5 points]
4. Sketch the reaction energy profile for an endothermic reaction and label the axis, activation energy of the forward reaction, activation energy of the backward reaction, and the change in enthalpy. [10 points]
5. If the rate of the combustion of ethane, C2 H6 , , what is __. [10 points]
Hint: write the balanced chemical equation of this reaction:
a.
b.
6. For the following hypothetical reaction: A --> B, what is the order of the reaction shown in the below graphs ? The value of the rate constants are not the same. Justify your answer. [10 points]
7. For the reaction: N2 + 3 H2 --> 2 NH3 , determine the rate law based on the following (hypothetical) experimental data (include the value & units for the rate constant). [15 points]
Expt[N2 ] (mM)
[H2 ] (mM)
1
1.0
1.0
4.74 * 10 -4
2
1.0
4.0
9.48 * 10 -4
3
2.0
9.0
28.44 * 10 -4
8. Describe the algebraic and graphical methods to determine the activation energy of a chemical reaction; include its basis (need not derive, but show setup and final outcome). [10 points]
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Nuclear chem. & kinetics retest [85 points] Honors chemistry
1. Write the nuclear equation for __ / fill-in the blank. [15 points]
a. beta decay of 17 O: ______________________________
b. fusion involving 7 Li & 17 O: __________________________
c. 6 Li + 18 O --> 11 B + _____; type of nuclear reaction = ____________
d. 235 Th --> 90 Sr + ____; type of nuclear reaction = ______________
e. gamma decay of 24 Na: _______________________
2. It take 5.0 years for a (hypothetical ?) radioactive isotope to decay from 25 mg to 21 mg. [10 points]
a. what is its decay constant ?
b. how much time would it take for this isotope to decay from 25 mg to 12.5 mg ?
3. A radioactive isotope has a half-life of 15 years. How much time would it take a 150 mg sample to become a 18.75 mg sample ? [5 points]
4. A chemical reaction generates 55 kJ / mol of heat and the activation energy of the forward reaction is 25 kJ / mole; what is the activation energy of the backward reaction ? sketch the reaction energy profile of this reaction and label the axis and the preceding energy terms on the graph. [10 points]
5. Describe how to differentiate between a 0th, 1st, and 2nd order reaction with a single reactant using graphical analysis. [15 points]
6. For the reaction: N2 + 3 H2 --> 2 NH3 , determine the rate law based on the following (hypothetical) experimental data (include the value & units for the rate constant) and determine the reaction rate in expt 4.
[20 points]
Expt[N2 ] (mM)
[H2 ] (mM)
1
2.0
2.0
4.74 * 10 -4
2
2.0
8.0
9.48 * 10 -4
3
4.0
18.0
28.44 * 10 -4
4
1.0
16.0
?
7. catalyst. [10 points]
a. what is a catalyst ? [4 points]
b. how does a catalyst produce its effect ? refer to the reaction energy profile, the Arrenhius equation, and the rate law in your response. [6 points]
