Answer:
B. 1.82(10³) seconds (1820 seconds)
Explanation:
Speed of Light: 3.00(10⁸) m/s or 3.00(10⁵) km/s
We know the distance from the Moon to Earth as 5.46(10⁸) km
We simply divide the distance by the speed of light:
We should get 1820 seconds or B. 1.82(10³) as our answer.
Answer : The initial mass of the sample is, 31.9 mg
Explanation :
Half-life = 4 days
First we have to calculate the rate constant, we use the formula :
Now we have to calculate the initial mass of sample.
Expression for rate law for first order kinetics is given by:
where,
k = rate constant =
t = time passed by the sample = 12 days
a = initial amount of the reactant = ?
a - x = amount left after decay process = 4 mg
Now put all the given values in above equation, we get
Therefore, the initial mass of the sample is, 31.9 mg