Answer:
A catalytic converter changes nitrogen dioxide to nitrogen gas and oxygen gas is a chemical change.
Explanation:
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In this case, since physical changes do not modify the molecular composition and structure of the material undergoing it whereas the chemical change does, for catalytic converters we should know they promote chemical reaction in which the composition is changed; for instance, for the given example, the following chemical reaction is the evidence:

As you can see, nitrogen and oxygen are no longer bonded but separated by themselves, therefore, this is a chemical change.
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Answer : The protons and neutrons subatomic particles will be located at Z.
Explanation :
In the model of an atom, there are three subatomic particles. Protons, neutrons and electrons are the subatomic particles.
The protons and the neutrons subatomic particles are located inside the nucleus and the electrons subatomic particle are located around or outside the nucleus.
The protons are positively charged, electrons are negatively charged and neutrons are neutral that means it has no charge.
In the given dartboard, Z is the nucleus in which the protons and neutrons subatomic particles are present and x, w & y are the electrons because they are located around the nucleus.
Hence, the protons and neutrons subatomic particles will be located at Z.
Answer: b). The B−A−B angles between neighboring B atoms are 90∘.
Explanation: The square planar geometry is the geometry in which the four groups are connected through an angle of 90∘ and all 5 atoms are in one plane.
It is not necessary for the molecule to have two non bonding pair of electrons on atom A but if it does have , then its parent geometry will be distorted octahedral. And if it doesn't have this non bonding pair of electrons then the geometry would be the square planar.
Thus the molecule has four electron domains about the central atom A if the parent geometry is square planar otherwise it would have 8 electron domain in distorted octahedral geometry.
True. The thing about chemical changes is that it is not easily reversible and new substances having different chemical properties are formed. For example; burning of wood to ashes.