Answer:
substance
Explanation:
A mixture is when two or more <u>different</u> atoms/molecules are together, but not joined.
A substance is when the <u>same </u>atom/molecule is in a group together.
In this example, it is a substance because it is comprised of the same molecule not joined all together. If you wanted a mixture, other colored atoms/molecule (e.g. add green atoms) would change it to this property.
Answer:
C. It may act as an insulator or a conductor.
Explanation:
Group B are the metalloids, so they have properties of both metals and nonmetals.
Answer:

Explanation:
Hello,
In this case, the molar enthalpy of reaction is obtained by dividing the involved energy by the reacting moles:

Thus, it is important to notice that the compound "uses" the energy, it means that it absorbs the energy, for that reason the sign is positive. Moreover, computing the result in kJ/mol we finally obtain:

Best regards.