Sodium chloride, methane gas and water
Use the formula for second order reaction:

C = concentration at time t
C0 = initial conc.
k = rate constant
t = time
1st equation :

2nd Equation:

Find

from 1st equation and put it in 2nd equation:


k = 0.046
The answer for the first question is A. Single covalent bond.
The answer for the second question is C. Carbon dioxide.