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3 years ago

What is the half-life of a 12 g sample of radioisotope that decayed to 6 g in 28

Chemistry

1 answer:

Charra [1.4K]3 years ago

4 0

Answer:

A. 28 years

Explanation:

Applying,

R = R'(2ᵃ/ⁿ).............. Equation 1

Where R = Original sample, R' = Sample left after decay, a = Total time taken to decay, n = half life.

From the question,

Given: R = 12 g, R' = 6 g, a = 28 years.

Substitute into equation 1 and solve for n

12 = 6(2²⁸/ⁿ)

12/6 = 2²⁸/ⁿ

2²⁸/ⁿ = 2

Equation the base,

28/n = 1

n = 28 years.

Hence the half-life is 28 years

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What is the relative atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances

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The given question is incomplete. The complete question is:What is the relative atomic mass of a hypothetical element that consists isotopes in the indicated natural abundances.

Isotope mass amu Relative abundance

1 77.9 14.4

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Express your answer to three significant figures and include the appropriate units.

Answer: 84.2 amu

Explanation:

Mass of isotope 1 = 77.9

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$\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})$

$A=\sum[(77.9\times 0.144)+(81.9\times 0.143)+(85.9\times 0.713)]$

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