It would take 147 hours for 320 g of the sample to decay to 2.5 grams from the information provided.
Radioactivity refers to the decay of a nucleus leading to the spontaneous emission of radiation. The half life of a radioactive nucleus refers to the time required for the nucleus to decay to half of its initial amount.
Looking at the table, we can see that the initial mass of radioactive material present is 186 grams, within 21 hours, the radioactive substance decayed to half of its initial mass (93 g). Hence, the half life is 21 hours.
Using the formula;
k = 0.693/t1/2
k = 0.693/21 hours = 0.033 hr-1
Using;
N=Noe^-kt
N = mass of radioactive sample at time t
No = mass of radioactive sample initially present
k = decay constant
t = time taken
Substituting values;
2.5/320= e^- 0.033 t
0.0078 = e^- 0.033 t
ln (0.0078) = 0.033 t
t = ln (0.0078)/-0.033
t = 147 hours
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Answer:
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If a piece of charcoal is taken and set on fire it will evolve CO2 and heat. Charcoal is solid but carbon dioxide is gaseous. This is an example of change of state and evolve of heat during chemical reaction.
Taking into account the definition of avogadro's number, 3.82×10⁻³ moles of H are 2.3×10²¹ particles of H.
<h3>
Avogadro's Number</h3>
Avogadro's Number or Avogadro's Constant is called the number of particles that make up a substance (usually atoms or molecules) and that can be found in the amount of one mole of said substance. Its value is 6.023×10²³ particles per mole. Avogadro's number applies to any substance.
<h3>This case</h3>
Then you can apply the following rule of three: if 6.023×10²³ particles are contained in 1 mole of H, then 2.3×10²¹ particles are contained in how many moles of H?
amount of moles of H= (2.3×10²¹ particles × 1 mole)÷ 6.023×10²³ particles
<u><em>amount of moles of H= 3.82×10⁻³ moles</em></u>
Finally, 3.82×10⁻³ moles of H are 2.3×10²¹ particles of H.
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