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arlik [135]
3 years ago
15

An unknown radioactive substance has a half-life of 3.20hours . If 46.2g of the substance is currently present, what mass A0 was

present 8.00 hours ago?Express your answer with the appropriate units.
Americium-241 is used in some smoke detectors. It is an alpha emitter with a half-life of 432 years. How long will it take in years for 34.0% of an Am-241 sample to decay?

Express your answer with the appropriate units.

A fossil was analyzed and determined to have a carbon-14 level that is 80% that of living organisms. The half-life of C-14 is 5730 years. How old is the fossil?

Express your answer with the appropriate units.
Chemistry
1 answer:
iogann1982 [59]3 years ago
7 0

Answer:

a) a0 was 46.2 grams

b) It will take 259 years

c) The fossil is 1845 years old

Explanation:

<em>An unknown radioactive substance has a half-life of 3.20hours . If 46.2g of the substance is currently present, what mass A0 was present 8.00 hours ago?</em>

A = A0 * (1/2)^(t/h)

⇒ with A = the final amount = 46.2 grams

⇒ A0 = the original amount

⇒ t = time = 8 hours

⇒ h = half-life time = 3.2 hours

46.2 = Ao*(1/2)^(8/3.2)

Ao = 261.35 grams

<em>Americium-241 is used in some smoke detectors. It is an alpha emitter with a half-life of 432 years. How long will it take in years for 34.0% of an Am-241 sample to decay?</em>  

t = (ln(0.66))-0.693) * 432 = 259 years

It will take 259 years

<em>A fossil was analyzed and determined to have a carbon-14 level that is 80% that of living organisms. The half-life of C-14 is 5730 years. How old is the fossil?</em>

<em />

t = (ln(0.80))-0.693) * 5730 = 1845

The fossil is 1845 years old

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Nadusha1986 [10]
Molar mass of 13c = 13 grams
number of moles = mass / molar mass
therefore,
number of moles = 7 / 13
To know the number of atoms in 7/13 moles, we simply multiply the number of moles by Avogadro's number as follows:
number of atoms = (7/13) x 6.022 x 10^23 = 3.2426 x 10^23 atoms
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A - Increase (R), Decrease (P), Decrease(q), Triple both (Q) and (R)

B - Increase(P), Increase(q), Decrease (R)

C - Triple (P) and reduce (q) to one third

Explanation:

<em>According to Le Chatelier principle, when a system is in equilibrium and one of the constraints that affect the rate of reaction is applied, the equilibrium will shift so as to annul the effects of the constraint.</em>

P and Q are reactants, an increase in either or both without an equally measurable increase in R (a product) will shift the equilibrium to the right. Also, any decrease in R without a corresponding decrease in either or both of P and Q will shift the equilibrium to the right. Hence, Increase(P), Increase(q), and Decrease (R) will shift the equilibrium to the right.

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