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Elden [556K]
3 years ago
6

How many milligrams of a 20mg sample of cesium-137 remain after 60 years

Chemistry
1 answer:
andrey2020 [161]3 years ago
5 0
Cs -137 has a half life of about 30 years. If 60 years pass, there is two half lives passed so 1/2 * 1/2= 1/4. Take 1/4 and multiply it with the mass given:
(1/4)*20mg=5mg left
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In terms of energy, how would you classify the following chemical reaction?
olga_2 [115]

1. Answer;

- Exothermic reaction

Explanation;

-Exothermic reactions are types of chemical reactions in which heat energy is released to the surroundings. Since enthalpy change is the difference between the energy of products an that of reactants. It means that in an exothermic reaction the energy of products is less than that of products. In this case an energy of 315kJ is released to the surroundings.

2. Answer;

Conserved

-The total amount of energy before and after a chemical reaction is the same. Thus, energy is conserved.

Explanation;

-According to the law of conservation of energy, energy is neither created nor destroyed. Energy may change form during a chemical reaction. For example, energy may change form from chemical energy to heat energy when gas burns in a furnace. However, the exact amount of energy remains after the reaction as before, which is true for all chemical reactions.

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Please Help Quick!!!<br><br> Lewis Structure of PO3 3-
nevsk [136]

1. Find its coordination figure/coordination number of central atom (CF)

Ev = Vallence electron of central atom

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charge = charge of the compound

2. Find EP (electron pairs) and LP (lone pairs)

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3. Draw the skeleton with octet substituents (top right figure)

4. Find formal charge for each atoms (Qf)

5. Write formal charge near atom in skeleton

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8 0
3 years ago
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Step (1):
Generation of electrophile: by the action of Lewis acid FeCl₃ on Cl₂ to serve as a source of Cl⁺ (Electrophile)
Step (2):
Addition of electrophile to form carbocation:
addition of electrophile to form C-Cl bond and form carbocation which is stabilized by resonance.
Step (3):
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8 0
3 years ago
If 45 mL of water are added to 250 mL of a 0.75 M K2SO4 solution, what will the molarity of the diluted solution be?
krok68 [10]

Answer:

\large\boxed{\large\boxed{0.64M}}

Explanation:

When you form a <em>diluted solution</em> from a mother (concentrated) solution, the moles of solute are determined by the mother solution.

The main equation is:

Molarity=\dfrac{\text{moles of solute}}{\text{volume of the solution in liters}}

Then, since the moles of solute is the same for both the mother solution and the diluted solution:

          \text{Molarity mother solution }\times\text{ volume mother solution}=\\\\=\text{Molarity diluted solution }\times\text{ volume diluted solution}

Substitute and solve for the molarity of the diluted solution:

           250mL\times 0.75M=(45mL+250mL)\times M\\\\\\M=\dfrac{250mL\times 0.75M}{295mL}=0.64M

8 0
3 years ago
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