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geniusboy [140]
2 years ago
8

A radioactive substance has a half-life of 5 million years. What is the age of a rock in which 25% of the original radioactive a

toms remain? You must show your work or explain how you came up with your answer for full credit.
Chemistry
1 answer:
GenaCL600 [577]2 years ago
5 0

Answer:

10 million years

Explanation:

For a sample to decay to 25% of its original amount, 2 half lives must have passed. Since one half life is 5 million years, multiplying this by 2 gives us that 2 half lives is 10 million years.

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Which metal is more active than H2?<br> (1) Ag (3) Cu<br> (2) Au (4) Pb
astraxan [27]

Answer is (4) - Pb.


According to the reactivity series of elements

- the elements which are above the hydrogen are more reactive than hydrogen.

- the elements which are below the hydrogen are less reactive than hydrogen.


Among the given choices, only Pb is placed above the hydrogen in the reactivity series and rest are below the hydrogen.


Hence, Pb is more active than hydrogen.

5 0
3 years ago
The half-life of radon-222 is 3.8 days. If a sample currently contains 3.1 grams of radon-222, how much radon-222 did this sampl
vodka [1.7K]

The   number  of grams of  radon 222 did it have 15.2  ago was  49.6 grams( answer  C)

 <u>calculation</u>

  • calculate the number of half life it has covered    from   15.2  days to 3.8 days

             that is  divide 15.2/ 3.8 = 4 half life

  •  half  life is time taken for a radio activity  of a specified isotope to fall to half its original mass

therefore  3.8 days ago  it was  3.1 x2 =  6.2 grams

                  7.6 days ago  it was 6.2 x2 = 12.4 grams

                   11.4  days  ago it was 12.4  x2=  24.8  grams

                  15.2  days  ago  it was  24.8 x2=49.6 grams





5 0
3 years ago
What are the moles of gas are in a 30 liter scuba canister if the temperature of the canister is 300 K and the pressure is 200 a
Lady_Fox [76]

Answer:

n = 243.605

Explanation:

Given

Pressure, P = 200\ atm

Temperature, T = 300k

Volume, V = 30L

Required

Calculate the number of moles

We'll apply the following formula to solve this question

n = \frac{pV}{RT}

Where

R = 0.0821 L\ atm/(mol\ K)

The above equation is an illustration of the ideal gas law

Substitute values for p, V, R and T in:

n = \frac{pV}{RT}

n = \frac{200 * 30}{0.0821 * 300}

n = \frac{6000}{24.63}

n = 243.605

<em>Hence, there are 243.605 moles</em>

7 0
3 years ago
Help now im not trying to fail
Alekssandra [29.7K]

Answer:

i cant see the whats in the picture

5 0
3 years ago
Read 2 more answers
What dissolved solid has the highest concentration in the ocean? sodium chloride
jeyben [28]

Answer:

chloride and sodium.

Explanation:

These two make up over 90% of all dissolved ions in seawater.

mark me brainliest

3 0
3 years ago
Read 2 more answers
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