Hiiiiiiiiiiiiiiiiiiiiiikiiiii
Answer : The concentration of A after 80 min is, 0.100 M
Explanation :
Half-life = 20 min
First we have to calculate the rate constant, we use the formula :



Expression for rate law for first order kinetics is given by:

where,
k = rate constant = 
t = time passed by the sample = 80 min
a = initial amount of the reactant = 1.6 M
a - x = amount left after decay process = ?
Now put all the given values in above equation, we get


Therefore, the concentration of A after 80 min is, 0.100 M
The answer is Doppler Radar. Hope this helps!
Phenolphthalein is an indicator used in chemistry to detect acidic or basic/alkaline solutions.It is often used in the lab as an indicator used to carry out accurate titration using soluble reactants.