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The half-life of strontium-90 is 28.1 years. Calculate the percent of a strontium sample left after 100 years.

Aliun [14]

Answer:

Option 4. 8.5%

Explanation:

The half-life time of a radiactive isotope (radioisotope) is a constant value, meaning that the amount of the radioisotope that decays will be (1/2) raised to the number of half-lives passed.

Naming A₀ the initial amount to the radioisotope, you can build this table to find the amount left.

Number of half-lives amount of radiosotope left

0 A₀

1 (1/2) × A₀

2 (1/2)×(1/2)×A₀ = (1/2)² × A₀

3 (1/2)³ ×A ₀

4 (1/2)⁴ × A₀

n (1/2)ⁿ × A₀

Now calculate the number of half-lives the strontium-90 sample has passed after 100 years:

n = 100 years / 28.1 years ≈ 3.5587

Hence, the amount of strontium-90 is:

$(\frac{1}{2})^{3.5587}A_0=0.08486A_0$

In percent, that is:

$(0.08486A_0/A_0).100=8.486%$

Rounding to two significant figures, that is 8.5%.

Conclusion: The percent of strontium-90 left after 100 yeaers is 8.5% (choice number 4).

6 0

4 years ago

How is the weathering of rocks by water different from the weathering of rocks by ice?

ehidna [41]

Answer:

The formation of ice can also break rocks. If water gets into a crack in a rock and then freezes, it expands and pushes the crack further apart. When the ice melts later, water can get further into the crack. When the water freezes, it expands and makes the crack even bigger.

Explanation:

6 0

3 years ago

Characteristics of α, β, and γ rays

Allisa [31]

Answer:

1. it is symbolized as 4/2 He : Alpha rays

2. it has the weakest penetrating power : Alpha rays

3. It is a high-speed electron : beta rays

4. It possesses neither mass nor charge : gamma rays

5. it has the strongest penetrating power : beta rays

6. its is symbolized as 0/-1e : beta rays

7. it is the most massive of all the components: alpha rays

Explanation:

Let us consider the characteristics of each of the given rays.

α rays: These are helium nucleus so are symbolized by $He^{4}_{2}$

Due to two protons and two neutrons unlike beta and gamma rays these are the most massive and thus have least penetrating power among the three given rays.

β rays: These are actually high speed electrons and are symbolized as $^{0}_{-1}e$ . Due to lesser mass than alpha rays they are more penetrating than them however less penetrating than gamma rays.