Question 54
1 answer:
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Answer : The time required for decay is, 84 days.
Explanation :
Half-life of chromium-51 = 28 days
First we have to calculate the rate constant, we use the formula :
Now we have to calculate the time required for decay.
Expression for rate law for first order kinetics is given by:
where,
k = rate constant
t = time taken by sample = ?
a = let initial activity of the sample = 100
a - x = amount left after decay process = 12.5
Now put all the given values in above equation, we get
Therefore, the time required for decay is, 84 days.
An isotope of ₂₀⁴⁰X ⇒₂₀⁴⁴X
<h3>Further explanation </h3>The elements in nature have several types of isotopes
Isotopes are atoms that have the same number of protons and a different number of neutrons.
So Isotopes are elements that have the same Atomic Number (Proton)
In the following element notation,
X = symbol of elemental atom
A = mass number
= number of protons + number of neutrons
Z = atomic number
= number of protons = number of electrons, on neutral elements
For symbol of isotope X :
₂₀X⁴⁰ : atomic number = 20, mass number = 40
A. ₄₀²⁰X : atomic number = 40, mass number = 20, neutrons=20
B. ₂₀⁴⁰X²⁺ : atomic number = 20, mass number = 40, neutrons=20
C. ₂₁⁴⁰X : atomic number = 21, mass number = 40, neutrons=19
D. ₂₀⁴⁴X : atomic number = 20, mass number = 44, neutrons=22