The first-order rearrangement of CH3NC is measured to have a rate constant of 3.61 x 10-15 s-1 at 298 K and a rate constant of 8
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The question is incomplete, here is the complete question.
If we start with 1.000 g of strontium-90, 0.805 g will remain after 9.00 yr. This means that the half-life of strontium-90 is ________ yr.
a. 28.8 b. 30.9 c. 35.4 d. 32.2
Answer : The half-life of strontium-90 is 28.8 years.
Explanation :
This is a type of radioactive decay and all radioactive decays follow first order kinetics.
First we have to calculate the rate constant.
Expression for rate law for first order kinetics is given by :
where,
k = rate constant
t = time taken for decay process = 9.00 year
a = initial amount or moles of the reactant = 1.000 g
a - x = amount or moles left after decay process = 0.805 g
Putting values in above equation, we get:
To calculate the half-life, we use the formula :
Therefore, the half-life of strontium-90 is 28.8 years.
Structure along with ¹H-NMR is shown below.
Signal for Hₐ;
Based on multiplicity of of the peak, a Singlet peak (the only singlet peak present in spectrum) at 2.2 ppm was assigned to Hₐ. As the methyl group in not coupling with any other proton so it gave a singlet peak.
Signal for Hb;
Based on multiplicity of of the peak, a Quartet peak (the only quartet peak present in spectrum) at 2.4 ppm was assigned to Hb. As the methylene group in coupling with methyl group having three protons so it gave a Quartet peak.
Signal for Hc;
Based on multiplicity of of the peak, a Triplet peak (the only triplet peak present in spectrum) at 1.1 ppm was assigned to Hc. As the methyle group in coupling with methylene group having two protons so it gave a Triplet peak.
Signal for Hₐ;
Based on multiplicity of of the peak, a Singlet peak (the only singlet peak present in spectrum) at 2.2 ppm was assigned to Hₐ. As the methyl group in not coupling with any other proton so it gave a singlet peak.
Signal for Hb;
Based on multiplicity of of the peak, a Quartet peak (the only quartet peak present in spectrum) at 2.4 ppm was assigned to Hb. As the methylene group in coupling with methyl group having three protons so it gave a Quartet peak.
Signal for Hc;
Based on multiplicity of of the peak, a Triplet peak (the only triplet peak present in spectrum) at 1.1 ppm was assigned to Hc. As the methyle group in coupling with methylene group having two protons so it gave a Triplet peak.