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OleMash [197]
3 years ago
5

Radium-221 has a half-life of 30 sec. How long will it take for 96% of a sample to decay?

Chemistry
1 answer:
monitta3 years ago
3 0
We can calculate how long the decay by using the half-life equation. It is expressed as:

A = Ao e^-kt

<span>where A is the amount left at t years, Ao is the initial concentration, and k is a constant.
</span><span>From the half-life data, we can calculate for k.
</span>
1/2(Ao) = Ao e^-k(30)
<span>k = 0.023
</span>
0.04Ao = Ao e^0.023(t)
<span>t = 140 sec</span>
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Analysis of an ore of calcium shows that it contains 13.61 g calcium and 21.77 g oxygen in a 46.28-g sample. Calculate the perce
kondor19780726 [428]

Answer:

29.41% of Calcium and 47.04% of Oxygen

Explanation:

The percent composition of an atom in a molecule is defined as 100 times the ratio between the mass of the atom and the mass of the molecule.

The mass of the molecule of the problem (Ore) is 46.28g. That means the percent composition of Calcium is:

13.61g / 46.28g * 100 = 29.41% of Calcium

And percent composition of Oxygen is:

21.77g / 46.28g * 100 = 47.04% of Oxygen

5 0
3 years ago
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Vladimir [108]

Answer:

Hey!

Your answer is Calcium Phosphate!

Explanation:

It is the substance/mineral that is mostly found in our teeth and bones!

HOPE THIS HELPS!!

7 0
3 years ago
What is newly formed land consisting of and arc shaped island chain called?
sweet [91]
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3 0
3 years ago
Which of the following statement is FALSE? a. Lowering the free energy of the transition state can increase a reaction rate. b.
ryzh [129]

Answer: Option (c) is the correct answer.

Explanation:

Activation energy or free energy of a transition state is defined as the  minimum amount of energy required to by reactant molecules to undergo a chemical reaction.

So, when activation energy is decreased then molecules with lesser amount of energy can also participate in the reaction. This leads to an increase in rate of reaction.  

Also, increase in temperature will help in increasing the rate of reaction.

Whereas at a given temperature, every molecule will have different energy because every molecule travels at different speed.

Hence, we can conclude that out of the given options false statement is that at a given temperature and time all molecules in a solution or a sample will have the same energy.

8 0
3 years ago
A gas takes up a volume of 35 L, and has a pressure of 4.8 atm. What is the new pressure of
joja [24]

Answer:

7.3 atm

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- Rearrange formula and then plug in values.

- Hope this helped! Let me know if you need more help or a further explanation.

3 0
3 years ago
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