How much of a 5.0 g sample of strontium-90 will remain after 87 years?

Answers

Answer 1

Answer: Since radioacitive decay fallows first order kinetics you can use the equation lnA(t)=-kt+lnA₀.
A₀=the initial amount of sample
A(t)=the amount of sample after t years
t=time
k=rate constant

First you need to solve for the rate constant (k) to get the equation
-((lnA(t)-lnA(0))/t=k which can simplify into k=-ln(A(t)/A₀)/t which can then be simplified further to ln(A₀/A(t))/t=k. I think the half life of strontium-90 is 28.8 years which means that when t=28.8 years, A(t) is going to equal 1/2 of A₀ and you can make the equation k=ln2/28.8 to get k=0.02408.

Now you need to solve for A(t) in the equation ln(A(t))=-kt+lnA₀ to get A(t)=e^(-kt+lnA₀) which simplifies to A(t)=A₀e^-kt. When you plug t=87, A₀=5g, and k=0.02408 into that equation you should get 0.616g.

Therefore after 87 years you will have 0.616g of strontium-90 if you started with a 5g sample.

I hope this helps. Let me know in the comments if anything is unclear.

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How will an energy diagram look for an exothermic reaction?The reactants and products will be at the same potential energy.

The reactants are at a higher potential energy compared to the products.

The reactants are at a lower potential energy compared to the products.

There will not be an activation energy barrier.

Answers

Answer : The correct option is, The reactants are at a higher potential energy compared to the products.

Explanation :

Exothermic reaction means energy is released and the overall enthalpy change is negative.

In exothermic reaction, the reactants are at a higher potential energy compared to the products. In other words, we can say that the products are more stable than the reactants.

B.) The reactants are at a higher potential energy compared to the products.

My reason being is because the reactants tend to gather "hyper" energy which is also known as potential energy and this will occur as shown in the answer as an Exothermic Reaction.

I really hope that this helps you out a lot. Have a nice day :)

From which of the following do spiral galaxies form? A.rapidly cooling protogalactic clouds
high-density protogalactic clouds
rapidly spinning protogalactic clouds
colliding/merging protogalactic clouds

Answers

The correct answer to the question that is stated above is the third option which is: rapidly spinning protogalactic clouds

One example of a spiral galaxy is the Milky Way. Spiral galaxies came from a rapidly spinning protogalactic clouds. Spiral galaxies form from the collapse of a protogalactic cloud.

What is the role of blood in the transportation of materials throughout the body

Answers

Blood carries hormones to specific organs.

Which types of reactions would result in the formation of precipitate?

Answers

Answer:

Double Displacement Reaction

Explanation:

A double displacement reaction is a type of chemical reaction in which the reactant ions exchange places to form new products. Usually, a double displacement reaction results in precipitate formation.

What is the energy needed to raise an electron in the hydrogen atom from the second energy level to the third energy level ?a.) 1.52x10^4 J b.) 3.63*10^-19 J c.) 2.18x10^-19 J d.) 4.48x10^-9 J e.) 3.03*10^-19J

Answers

$3.03*10^-19J$ is the energy needed to raise an electron in the hydrogen atom from the second energy level to the third energy level.

What are Energy Levels?

The electrons that surround an atom around the nucleus are located in regions called "energy levels". It represents the 3-D space that surrounds the nucleus where the electrons are present. It is divided into several energy levels such as first energy level, second energy level and so on.

The level that is closest to the nucleus is the first energy level, then the second one is further away from it, then the third one is a little further away and so on. Each energy level has different number of electrons like first has 2 electrons, second has 8, third has 8 and so on. The electrons which are further away from the nucleus are called valence electrons.

For given above information,

E = - $E_o$ / $n^2$

where,

$E_o$ = 13.6 eV (1 eV = 1.602×10-19 Joules) and n = 1,2,3… and so on so that the ground state has energy $E_1$ = -13.6 eV and the second energy level (the first excited state) has energy $E_2$ = -13.6/4 eV = -3.4 eV.

So,

1eV = 1.602× $10^-^1^9$ J

Energy difference can be calculated by -13.6eV ( $1/$ $n^3_f$ - $1/n^2_i$ )

$n_f$ = Final energy; $n_i$ = Initial energy

1.88 eV is equals to x

So, x= 3.03* $10^-^1^9$

Thus, $3.03*10^-19J$ is the energy needed to raise an electron in the hydrogen atom from the second energy level to the third energy level.

Learn more about Energy Level, here:

brainly.com/question/17396431

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The value of ΔH° for the reaction below is -126 kJ. The amount of heat that is released by the reaction of 25.0 g of Na2O2 with water is __________ kJ. 2Na2O2(s) + 2H2O(l) → 4NaOH(s) + O2(g) The value of ΔH° for the reaction below is -126 kJ. The amount of heat that is released by the reaction of 25.0 g of Na2O2 with water is __________ kJ. 2Na2O2(s) + 2H2O(l) → 4NaOH(s) + O2(g) 40.4 80.8 -126 67.5 20.2