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KIM [24]
2 years ago
15

You have 500,000 atoms of a radioactive substance. After 2 half-lives have past, how many atoms remain?

Chemistry
2 answers:
Aleonysh [2.5K]2 years ago
3 0

Answer:

125000

Explanation:

Because it is halved and halved again.

solong [7]2 years ago
3 0
Half life - when half of the radioactive substance has become stable

500,000/2 = 250,000 remaining after the first half life

250,000/2 = 125,000 remaining after the second


Or alternatively 1/4 x 500,000 = 125,000
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Assume that silver and gold form ideal, random mixtures. Calculate the mass of pure Ag needed to cause an entropy increase of 20
KengaRu [80]

Answer:

m_{Ag}=2,265.9g

Explanation:

Hello!

In this case, since the definition of entropy in a random mixture is:

\Delta S=-n_TR\Sigma[x_i*ln(x_i)]

For this silver-gold mixture we write:

\Delta S=-(n_{Au}+n_{Ag})R\Sigma[\frac{n_{Au}}{n_{Au}+n_{Ag}} *ln(\frac{n_{Au}}{n_{Au}+n_{Ag}} )+\frac{n_{Ag}}{n_{Au}+n_{Ag}} *ln(\frac{n_{Ag}}{n_{Au}+n_{Ag}} )]

By knowing the moles of gold:

n_{Au}=100g*\frac{1mol}{197g} =0.508mol

It is possible to write the aforementioned formula in terms of the variable x representing the moles of silver:

20\frac{J}{mol}=-(0.508+x)8.314\frac{J}{mol*K} \Sigma[\frac{0.508}{0.508+x} *ln(\frac{0.508}{0.508+x} )+\frac{x}{0.508+x} *ln(\frac{x}{0.508+x} )]

Which can be solved via Newton-Raphson or a solver software, in this case, I will provide you the answer:

x=n_{Ag}=21.0molAg

So the mass is:

m_{Ag}=21.0mol*\frac{107.9g}{1mol}\\ \\m_{Ag}=2,265.9g

Best regards!

3 0
3 years ago
What is the balanced equation for Al+FeN2>AlN+Fe
STALIN [3.7K]

Answer:2 AL + FEN2 = 2 ALN + FE

Explanation: AL might be an improperly capitalized: Al. One of your compounds is AL (A and L). Did you mean Al (aluminum)?

FEN2 might be an improperly capitalized: FeN2. ALN might be an improperly capitalized: AlN

FE might be an improperly capitalized: Fe

3 0
4 years ago
thermal windows often have all the air pumped out between the panes and a gas pumped in that is not harmful and wont react with
Ivenika [448]
C. Ar or Argon

<span>It is the most commonly used gas between thermal window panes. Argon has 34% lower thermal conductivity than air and is therefore more suitable to be used instead of air. It is also inert and does not react or causes any form of harm.</span>
4 0
3 years ago
What intramolecular bonds does H2 have
posledela
Covalent. The two hydrogen atoms share their electrons such that both outer shells are filled.
6 0
3 years ago
Read 2 more answers
1- What are the two types of neurons?
fomenos
Question #1

One kind of neuron would be known to be called a "<span>Sensory Neuron". This kind of neuron would be a kind that would send messages to your 5 senses. Which, when speaking about a human, this would therefore be our eyes, mouth, hearing, feel, and smell. This kind of neuron would send direct messages.

For example: My mother is cooking 'good o' brownies" in the kitchen. My "sensory neuron" would then smell these brownies, and then as I would smell it, I would then understand what is cooking. Therefore, this would then be an example of what this kind of neuron would then do.

(second neuron)

Now when speaking about a "motor neuron", this kind would then be the kind that would send the information OUT of the nerve system, not going INSIDE of the system, but it would be going outside of the body. And as this information would then leave and then go into the muscle or also the glands of the nerve system.

Question #2

</span><span>Which type of neuron is activated when you spontaneously withdraw your hand when it touches something hot?
</span>
This kind of neuron would be the kind neuron that would be known to be called "sensory neuron".

Let's consider: We would have to remember, sensory would be how you would feel, your sense on matter. And in this case, this person would be feeling her senses as she would be (touching something hot). And therefore, this would be known to be a "sensory neuron".
7 0
3 years ago
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