Answer:
a) a0 was 46.2 grams
b) It will take 259 years
c) The fossil is 1845 years old
Explanation:
<em>An unknown radioactive substance has a half-life of 3.20hours . If 46.2g of the substance is currently present, what mass A0 was present 8.00 hours ago?</em>
A = A0 * (1/2)^(t/h)
⇒ with A = the final amount = 46.2 grams
⇒ A0 = the original amount
⇒ t = time = 8 hours
⇒ h = half-life time = 3.2 hours
46.2 = Ao*(1/2)^(8/3.2)
Ao = 261.35 grams
<em>Americium-241 is used in some smoke detectors. It is an alpha emitter with a half-life of 432 years. How long will it take in years for 34.0% of an Am-241 sample to decay?</em>
t = (ln(0.66))-0.693) * 432 = 259 years
It will take 259 years
<em>A fossil was analyzed and determined to have a carbon-14 level that is 80% that of living organisms. The half-life of C-14 is 5730 years. How old is the fossil?</em>
<em />
t = (ln(0.80))-0.693) * 5730 = 1845
The fossil is 1845 years old
A, because the number of valence shell electrons (outer shell electrons) tells us how much the element or compound wants to bond or give up electrons. Most compounds and elements want to have eight valence ectrons in it's outer ring. So if an atom is far away from having eight, it will want to react more often.
We’re going to use the mass percent formula shown below:
For the percent by mass N, we’re going to rewrite the equation as:
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Problem Details
Calculate the mass percent composition of nitrogen in each nitrogen-containing compound:
c. NO2
Answer:
1 mol of water is produced in those conditions.
Explanation:
The reaction to produce water between H₂ and O₂ is this:
2H₂ + O₂ → 2H₂O
We don't have the amount of hydrogen, so we have to think that is in excess.
Let's work with oxygen.
Ratio is 1:2
For 0.5 mole of oxygen, I will make the double of moles of water.
The Environmental Protection Agency suggests using cold tap water for cooking instead of starting with warm tap water is because our drinking water is made out lead pipes, which is a serious risk to health.
Explanation:
- Lead is found throughout the environment in lead found in paint, air, soil, food and water.
- Lead can pose a significant risk to your health if too much of it enters your body.
- Lead enters drinking water primarily as a result of the corrosion.
- It also contains in materials containing lead like in the water distribution system and household plumbing.
- Lead in drinking rarely cause of lead poisoning can significantly increase a person’s total lead exposure.
- In particular the exposure of infants who drink baby formulas and concentrated juices that are mixed with water.
- EPA estimates that drinking water can make up to 20% or more of a person’s total exposure to lead which is dangerous.
