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ozzi
3 years ago
14

The decay of a radioactive material is monitored using a Geiger counter. At the start, the count rate is 2000 decays/minute. Fou

r hours later the decay rate is 500 counts/min. What is the half-life of the material?
Chemistry
1 answer:
Marat540 [252]3 years ago
5 0

Answer:

The half-life of the material is 2 years

Explanation:

Given;

initial count rate = 2000 decays/minute

final count rate =  500 counts/min

decay time = Four hours

To determine the half life of the material; we create a simple decay table that matches the decay time and count rates.

time (years)                     count rate

0                                    2000 decays/minute

2                                     1000 decays/minute

4                                     500 decays/minute

Half life is the time intervals = 2 years

Also using a formula;

N = \frac{N_o}{(t/2)^2} \\\\N_o-is \ the \ initial \ count\ rate\\\\N-is \ the \ final \ count\ rate\\\\t/_2 - is \ the\ half\ life \\\\N = \frac{N_o}{(t/2)^2} \\\\500 = \frac{2000}{(t/2)^2}\\\\(t/_2)^2 = \frac{2000}{500} \\\\(t/_2)^2 = 4\\\\t/_2 = \sqrt{4} \\\\t/_2 = 2 \ years

Therefore, the half-life of the material is 2 years

                                                               

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The box shows the element nitrogen as it appears in the
ozzi

Answer:

Option D. Electron clouds with a total of 7 electrons.

Explanation:

For an atom to be neutral (i.e having a charge of zero), the number of protons and electrons must be equal.

Thus, to know which option is correct, we shall determine the number of protons and electrons in the nitrogen atom as given in the question above.

From the question given above, we obtained the following:

Atomic number = 7

Mass number = 14

Number of protons =?

Number of electrons =.?

Next, we shall determine the number of protons in the nitrogen atom as follow:

Atomic number of an element is simply defined as the number of protons in the atom of the element. Mathematically,

Atomic number = proton number

Atomic number = 7

Therefore,

Number of protons = 7

Next, we shall determine the number of electrons in nitrogen atom as follow:

Since the atom is neutral (i.e having a charge of zero), the number of protons and electrons are equal i.e

Number of protons = number of electrons

Number of protons = 7

Therefore,

Number of electrons = 7

Thus, the nitrogen atom must have 7 electrons in order for it to be neutral.

**** Check ****

Charge of atom = Proton – Electron

Charge = 0

Proton = 7

Electron = 7

Charge of atom = Proton – Electron

0 = 7 – 7

0 = 0

8 0
3 years ago
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Bad White [126]
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3 0
3 years ago
How is pascals law used in the brakes of a car? <br><br> I’m giving 67 points!
bogdanovich [222]

Answer:

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8 0
3 years ago
if you have an isotope of the element carbon that has the mass number of 14, what other information would help you determine the
storchak [24]
Isotopes are forms of the same elements which contain equal number of protons but different number of nucleus in their nuclei, thus the differ in relative atomic mass but they have same chemical properties. The mass number is the summation of number of proton and number of neutron of an atom. If the mass number is known, then one need to know the number of proton in the atom in order to calculate for the number of neutron.
7 0
3 years ago
How many molecules of nitrogen are in 1.25 mol N2?
Anna [14]

Answer:

7.52 x 10²³ molecules N

Explanation:

multiply 1.25 mol of N2 by Avogadro's Number

5 0
3 years ago
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