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.
For what? what is your question
Answer: Option (d) is the correct answer.
Explanation:
An equation in which electrolytes are represented in the form of ions is known as an ionic equation.
Strong electrolytes easily dissociate into their corresponding ions. Hence, they form ionic equation.
is a strong acid and
is a strong bases, therefore, both of them will dissociate into ions.
Thus, total ionic equation will be as follows.

Answer:
a.
Explanation:
At 28 degrees highest line is CaCl2. Answer a.
Answer:
C
Explanation:
Only this choice is applicable and correct.
The inter-molecular forces of attraction between the molecules must have been broken (overcome) before the molecules can gain an increase in the kinetic energies between them.