Answer:
The concentration would be; 0.0038 μgmL
Explanation:
Half life, t1/2 = 68 minutes
Initial Conc. [A]o = 0.12/μgmL
Final Conc [A] = ?
Time. k = 340 minutes
ln[A] = ln[A]o - kt
t1/2 = ln2 / k
k = 0.693 / t1/2 = 0.693 / 68 = 0.01019
ln[A] = ln (0.12) - 0.01019 (340)
ln[A] = -2.1203 -3.4646
ln[A] = -5.5849
[A] = 0.00375 ≈ 0.0038 μgmL
Option 2: 12.0 L of
at STP.
The standard pressure and temperature values are 1 atm and 273.15 K.
Using the ideal gas equation, number of moles of gas can be calculated which is as follows:
PV=nRT...... (1)
Here, P is pressure, V is volume, n is number of moles, R is gas constant and T is temperature.
Also, in 1 mole of any gas there are
molecules of the gas. This is known as Avogadro's number and denoted by symbol 
Thus,

Equation (1) can be rewritten as follows:

On rearranging,

Here, all the other terms are constant except volume, thus, gas with volume equal to the volume of
will have same number of molecules.
Volume of
gas and
gas is same thus,
will have same total number of molecules as
gas.