Answer:
C₂H₄O
CH₃CHO
Explanation:
I'm not sure if you want the molecular formula or the condensed structure, but I will give you both.
Molecular formula:
You have 2 carbons (C₂), 4 hydrogens (H₄), and 1 oxygen (O). The molecular formula will be C₂H₄O.
Condensed Structure:
You have a carbon bonded to three hydrogens (CH₃). This carbon is bonded to a carbon that is bonded to a hydrogen and oxygen (CHO). The condensed structure will be CH₃CHO.
As long as the equation in question can be expressed as the sum of the three equations with known enthalpy change, its 
can be determined with the Hess's Law. The key is to find the appropriate coefficient for each of the given equations.
Let the three equations with given be denoted as (1), (2), (3), and the last equation (4). Let 
, 
, and 
be letters such that 
. This relationship shall hold for all chemicals involved.
There are three unknowns; it would thus take at least three equations to find their values. Species present on both sides of the equation would cancel out. Thus, let coefficients on the reactant side be positive and those on the product side be negative, such that duplicates would cancel out arithmetically. For instance, 
shall resemble the number of 
left on the product side when the second equation is directly added to the third. Similarly
Thus
and
Verify this conclusion against a fourth species involved- 
for instance. Nitrogen isn't present in the net equation. The sum of its coefficient shall, therefore, be zero.
Apply the Hess's Law based on the coefficients to find the enthalpy change of the last equation.
The right answer for the question that is being asked and shown above is that: "C. carbon and hydrogen." The pair of elements is MOST likely to chemically combine and form ionic bonds are <span>carbon and hydrogen </span>
The energy of 393 kJ is released as heat. Then, the container will experience an increase of temperature and, given that it is sealed, also an increase of pressure.
The increase of temperature results from the heat developed during the reaction.
The increase of pressure results from the fact that that the solid carbon will become gaseuos carbon dioxide. This gas will occupy a larger volume than the solid carbon and also this elevation of the temperature will make the pressure of the gas inside the container increase.
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