You fill a tank with gas at 30°c and 101.5 kpa and seal it. you decrease the temperature to 10°c but keep the volume constant. what happens to the pressure? (careful!

Assume that the gas that fills the tank is ideal for us to be able to use the ideal gas law. 
                                 PV = nRT
When V, n, and R are all constant, we can say that,
                               (T1)(P2) = (T2)(P1)
We convert temperature into kelvin (This is the portion where we have to be very careful not using the degrees Celsius).
                                (30 + 273)(P2) = (10 + 273)(101.5 kPa)
The value of P2 is 94.8 kPa.

The correct answer is Option A.

Explanation:

All the radioactive decay processes follows first order kinetics.

To calculate the rate constant for a reaction, we use the equation:

where,

k = rate constant for a reaction

= half life of a reaction = 14 days

Putting all the values in above equation, we get:

To calculate the amount of sample left, we use the equation:

where,

N = amount of sample left after time 't'

= initial amount of the sample = 124 mg

k = rate constant of the reaction =

t = time taken = 56 days

Putting values in above equation, we get:

Hence, the correct answer is Option A.