Answer:
4. Option C. Pentane.
5. Option D.
Explanation:
4. Hydrocarbons are compound containing carbon and hydrogen only. Hydrocarbons are said to be saturated when they contain only carbon to carbon single bond. All alkanes are saturated hydrocarbon.
The correct answer is pentane.
5. Isomerism is the phenomenon whereby two or more compounds have the same molecular formula but different structural patterns. The compounds involved are called isomers.
A careful observation of the diagram above shows that only option D satisfied the definition of Isomerism as the two compound both have the same molecular formula as C3H8O but different structural patterns.
Note: option C does not contain isomers as Isomerism can not occur in a compound having just 1 carbon atom.
A compound is where two or more elements have chemically bonded, and a mixture is where there are two or more elements are grouped together, but they are not chemically bonded.
An example of a mixture would be salt dissolved in water, and an example of a compound would be water (which is made up of 2 Hydrogen and 1 Oxygen bonded together)
tl;dr: I would go with B, basically.
Answer:

This is a double displacement reaction, C goes with Cl in the products side and O2 goes with H. All that is left is to balance the equation, making sure each side has equal amounts of atoms.
Answer:
3) O(g) is an intermediate; 2O3(g)→3O2(g)
Explanation:
The decomposition of ozone to yield oxygen occurs in a sequence of steps. The various non-elementary reactions involved constitute the reaction mechanism. In the sequence of reaction steps O(g) serves as an intermediate.
The overall reaction involves the conversion of two moles of ozone to three moles of oxygen as shown in the answer. Thus the O(g) is merely a reaction intermediate.