You got the questions correct
Answer:
Gasoline
Explanation:
Pure Substance: are those having same type of atoms or molecules.
Compound: one or more atoms of the element combine to form a compound.
Mixture: is combination of one or more substances mix together.
Homogeneous Mixture: are those which are not distinguish by naked eye but can be separated into its components by physical means
Heterogeneous mixture: are those which can be distinguishing by naked eye and can be separated into its components by physical means.
So keeping in mind the above definitions
Table salt:
The chemical formula of table salt is NaCl and it a pure compound not mixture.
Gasoline:
Gasoline is mixture of hydrocarbon, It contains small hydrocarbons ranging from 4 Carbon to 12 Carbon per molecule. it is a homogeneous mixture.
Aluminum:
Aluminum is a pure substance that is made up of same kind of atoms. so it is an element and not mixture. Its symbol is Al
Carbon dioxide:
Carbon dioxide is a pure compound and its chemical formula is CO₂ and not a mixture.
So, the write option is Gasoline.
Effects of changes in volume in a reversible reaction in a chemical equilibrium can be predicted using Le Chatelier's Principle. I think this might be the answer, I hope it helps.
Answer: The energy of an electron in the n = 2 level of a hydrogen atom is 3.40 eV.
Explanation:
Given: n = 2
The relation between energy and 
orbit of an atom is as follows.
Substitute the values into above formula as follows.
The negative sign indicates that energy is being released.
Thus, we can conclude that the energy of an electron in the n = 2 level of a hydrogen atom is 3.40 eV.
The postulates of Dalton's theory were:
1) Elements are made of extremely small particles called atoms
2) <span>Atoms of a given element are identical in size, mass, and other properties
</span>3) <span>Atoms cannot be subdivided, created, or destroyed</span>
4) Atoms combine in whole number ratio to form compounds
5) Chemical reactions are the rearrangement of atoms
The third postulate has been disproved by modern science, in which the atom has been split and been subdivided into smaller parts such as the neutron, proton and electron, which are further subdivided into quarks, gluons, and kaons.
The second postulate was also disproved upon the discovery of isotopes.
