Have a wonderful day :) thanks for the points
Answer : The time taken by the reaction is 
Explanation :
The expression used for second order kinetics is:
![kt=\frac{1}{[A_t]}-\frac{1}{[A_o]}](https://tex.z-dn.net/?f=kt%3D%5Cfrac%7B1%7D%7B%5BA_t%5D%7D-%5Cfrac%7B1%7D%7B%5BA_o%5D%7D)
where,
k = rate constant = 
t = time = ?
= final concentration = 0.40 M
= initial concentration = 2.16 M
Now put all the given values in the above expression, we get:


Therefore, the time taken by the reaction is 
Answer:
V = 267.2 L
Explanation:
Given data:
Volume of balloon = ?
Mass of helium = 2.50 g
Temperature of gas = 180°C
Pressure = 0.87 atm
Solution:
Number of moles of helium:
Number of moles = mass/molar mass
Number of moles = 2.50 g/ 4 g/mol
Number of moles = 0.625 g
Volume of helium:
PV = nRT
R = general gas constant = 0.0821 atm.L/mol.K
0.87 atm× V = 0.625 mol × 0.0821 atm.L/mol.K×453 K
V = 232.45 atm.L /0.87 atm
V = 267.2 L