What is the half-life of a radioisotope if 25.0 grams of an original 200.-gram sample of the isotope remains unchanged after 11.46 days?(1) 2.87 d (3) 11.46 d
(2) 3.82 d (4) 34.38 d
Answers
Answer : The correct option is, (2) 3.82 d
Solution : Given,
As we know that the radioactive decays follow first order kinetics.
So, the expression for rate law for first order kinetics is given by :
where,
k = rate constant
t = time taken for decay process = 11.46 days
a = initial amount of the reactant = 200 g
a - x = amount left after decay process = 25 g
Putting values in above equation, we get the value of rate constant.
Now we have to calculate the half life of a radioisotope.
Formula used :
Putting value of 'k' in this formula, we get the half life.
Therefore, the half-life of a radioisotope is, 3.820 d
2. 11.46/3=3.82
The answer is (2).
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blue end of the spectrum
middle of the spectrum
The light-gathering capacity of a telescope is dependent upon the:
magnification
focal length
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Answers
Answer:
1) blue end of the spectrum
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Explanation:
1) The electromagnetic spectrum encompases a wide range of frequency (ν) and wavelength (λ) that includes gamma rays, x-rays, ultra violet(UV), visible, infra red (IR), microwaves and radiowaves. The wavelength increases from gamma rays to radio waves.
The wavelength perceivable by human eyes lies in the UV-visible region which extends from 380 nm in the blue to 740 nm in the red.The shortest wavelengths occur in the blue end of the spectrum which also have the highest energy. In contrast, longer wavelengths occur on the red which have lower energy.
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Answers
Answer:
The answer to your question is carbon. The masses of all isotopes are based on a comparison to the mass of a particular isotope of carbon123. This isotope is carbon-12, which has six protons and six neutrons in its nucleus. By definition, one atom of carbon-12 is assigned a mass of exactly 12 atomic mass units (amu), which is a unit of mass equal to one twelfth of an atom of carbon-1212. All other isotopes have their masses expressed as a fraction or a multiple of this standard unit. For example, the isotope hydrogen-1 has a mass of 1.0078 amu, which means it is slightly heavier than one twelfth of carbon-12. The isotope uranium-238 has a mass of 238.0508 amu, which means it is almost 20 times heavier than carbon-12. The reason why carbon-12 was chosen as the reference standard is because it is abundant, stable, and easy to measure3. I hope this answer helps you understand the concept of isotopes and atomic mass better.