<u>Answer:</u>
<em>One mole of a substance forms Instead of standard atmospheric pressure and temperature from its pure elements{ conditions being the same} then this change and enthalpy is known as </em><em>enthalpy of formation.</em>
<u>Explanation:</u>
The equation of this formation can let us know what actually happens
ΔH = ΔHf(products) - ΔHf (reactants)
Hence we can say this change in enthalpy formation is the difference between the sum of product and sum of reactants.
The question is incomplete, here is the complete question:
If you performed a combustion reaction of 2-ethyl-1-methylpropene, what products would you expect to be present?
Answer: The products of the combustion of 2-ethyl-1-methylpropene are carbon dioxide and water.
<u>Explanation:</u>
Combustion reaction is defined as the reaction in which a hydrocarbon reacts with oxygen gas to produce carbon dioxide gas and water molecule.

We are given a chemical compound, which is 2-ethyl-1-methylpropene. The chemical formula of this compound is 
The chemical equation for the combustion of 2-ethyl-1-methylpropene follows:

By Stoichiometry of the reaction:
4 moles of 2-ethyl-1-methylpropene reacts with 37 moles of oxygen gas to produce 24 moles of carbon dioxide and 26 moles of water
Hence, the products of the combustion of 2-ethyl-1-methylpropene are carbon dioxide and water.
1.Atoms combine to form molecules which in turn are what makes up matter.
2.Electrons carry negative charges and protons carry positive charges. While protons have far more mass the number of protons and electrons in a stable atom is the same. These charges cancel each other out. If there is an imbalanced then the atom is radioactive and decays until it reaches stability.
3.According to the kinetic theory of matter, "<span>All matter is made up of atoms and molecules that are constantly moving. When heat is added to a substance, the molecules and atoms vibrate faster. As atoms vibrate faster, the space between atoms increases."</span>
Answer:
B is the correct answer.
......Hopefully it it helpful.......