Nitrogen dioxide undergoes thermal decomposition according to the second-order reaction 2 NO2(g) → 2 NO(g) + O2(g). When 0.700 M NO2 is allowed to react for 90.0 seconds, its concentration falls to 0.0463 M. What is the rate constant for the reaction?

K = 0.2241 M-1 s-1

Explanation:

∴ a: NO2

∴ α = 2 second order

⇒ - δCa/δt = K Ca²

⇒ - ∫δCa/Ca² = K*∫δt

⇒ [ 1/Ca - 1/Cao ] = K*t

∴ Ca = 0.0463 M

∴ Cao = 0.700 M

∴ t = 90.0 s

rate constant (K):

⇒ - [ 1/0.0463 - 1/0.700 ] = K*(90.0 s)

⇒ 20.1697 M-1 = K*(90.0 s)

⇒ K = 0.2241 M-1 s-1

the answer to your question is c

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.