Answer:

Explanation:
As we know by radioactivity law

so here we will have


now we will have


now we also know that



Answer:

Explanation:
From the question we are told that:
Mass of block 
Temperature of block 
Volume of water 
Temperature of water 
Density of water 
Specific heat of water 
Specific heat of copper 
Generally the equation for equilibrium stage is mathematically given by









Answer : The time passed in years is 20.7 years.
Explanation :
Half-life = 28.1 years
First we have to calculate the rate constant, we use the formula :



Now we have to calculate the time passed.
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = 
t = time passed by the sample = ?
a = initial amount of the reactant = 1.00 g
a - x = amount left after decay process = 0.600 g
Now put all the given values in above equation, we get


Therefore, the time passed in years is 20.7 years.