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Lelu [443]
3 years ago
9

What is the half-life of an isotope that decays to 6.25% of its original activity in 18.9 hours?

Chemistry
1 answer:
inessss [21]3 years ago
8 0
Radioactive material obeys 1st order decay kinetics,
For 1st order reaction, we have 
k = \frac{2.303}{t}Xlog \frac{\text{initial conc.}}{\text{final conc.}}
where, k = rate constant of reaction

Given: Initial conc. 100, Final conc. = 6.25, t = 18.9 hours

∴ k = \frac{2.303}{18.9} X log \frac{100}{6.25} = 0.1467 hours^(-1)

Now, for 1st order reactions: half life = \frac{0.693}{k} =  \frac{0.693}{0.1467} = 4.723 hours.


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If 450.0 mL of a 0.500 M solution is mixed with 200.0 mL of water, what is the molarity of the new
Oksana_A [137]

Answer:

Answer: A) .346 M

Explanation:

Given:

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1) Convert mL to L

450 mL = .45 L

200 mL = .2 L

2) Find mols in solution

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x = .225 mol

3) Find total volume of solution

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y = .225 mol (from step 2)/ .65 L (from step 3)

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Answer: A) .346 M

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How many molecules are there in 3 moles of aluminum chloride ?
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2 years ago
Bond order of n2<br><br>bond order of N2 ​
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