The question is incomplete, here is the complete question:
At elevated temperature, nitrogen dioxide decomposes to nitrogen oxide and oxygen gas

The reaction is second order for
with a rate constant of
at 300°C. If the initial [NO₂] is 0.260 M, it will take ________ s for the concentration to drop to 0.150 M
a) 1.01 b) 5.19 c) 0.299 d) 0.0880 e) 3.34
<u>Answer:</u> The time taken is 5.19 seconds
<u>Explanation:</u>
The integrated rate law equation for second order reaction follows:
![k=\frac{1}{t}\left (\frac{1}{[A]}-\frac{1}{[A]_o}\right)](https://tex.z-dn.net/?f=k%3D%5Cfrac%7B1%7D%7Bt%7D%5Cleft%20%28%5Cfrac%7B1%7D%7B%5BA%5D%7D-%5Cfrac%7B1%7D%7B%5BA%5D_o%7D%5Cright%29)
where,
k = rate constant = 
t = time taken = ?
[A] = concentration of substance after time 't' = 0.150 M
= Initial concentration = 0.260 M
Putting values in above equation, we get:

Hence, the time taken is 5.19 seconds
does it have multiple choice
Answer:
This question is incomplete
Explanation:
There are two major forms of energy; these are potential and kinetic energy. Kinetic energy is the energy present in moving options. Examples include mechanical and electrical energy.
The formula for kinetic energy is 1/2mv² where "m" is mass and "v" is velocity.
While potential energy is the energy present in stationary objects that can be put to use in future. Example includes a ball in its resting state. The formula for potential energy is "mgh" where "m" is mass, "g" is acceleration due to gravity and "h" is height
Considering the law of conservation of energy which states that energy can neither be created nor destroyed but can be transformed from one form to another. Looking at the example provided earlier for potential energy, a ball in its resting position (having a potential energy) when kicked will have a kinetic energy (which can be calculated with the formula provided earlier), hence
Total energy = potential energy (P.E) + kinetic energy (K.E)
This formula and the explanation above can be used to answer the completed question.
NOTE: There is no standard relationship between P.E and K.E. They could be directly or indirectly proportional depending on the circumstance.
Answer:
SrSO4
Explanation:
According to solubility rules, we know that the sulphates of the elements of group two are insoluble in water. The solubility rules describe what chemical species are soluble in water and what species are not soluble in water.
Generally, all chlorides are soluble in water with exception of chlorides such as silver chloride. The chlorides of group one elements are usually highly soluble in water.
Since SrSO4 is a sulphate of a group two element (strontium) it will be the insoluble solid product of the double displacement reaction described in the question.
A is correct. water is incompressible, so it will always have the same density, regardless of volume