Which of the following statements is true of combustion reactions? A. Hydrogen gas (H2) must be one of the reactants

B. Water (H2O) is always a product

C. Energy is released by the reaction

D. Carbon monoxide (CO2) is always produced


Answer 1

Gasoline contains C and H atoms. During combustion, the carbon (C) from the fuel combines with oxygen (O2) from the air to produce carbon dioxide (CO2).
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O.

Combustion reactions release large amounts of heat. They have negative enthalpy. A negative enthalpy represents an exothermic reaction, releasing heat. This reaction is spontaneous and exothermic, since we can obtain energy from the reaction; the ΔG (free energy) is negative (So 1 is true).

ΔG < 0, so the free energy of the system decreases with the reaction. Remember that when there is a negative ΔG the reaction goes from higher free energy to lower free energy, like in this case.

Answer 2

Answer: Option (B) is the correct answer.


A chemical reaction in which a hydrocarbon combines with oxygen atom that is present in air to yield carbon dioxide and water along with the products.

For example,

Here, methane undergoes combustion reaction to yield carbon dioxide and water as the products.

Hence, we can conclude that the statement water () is always a product, is true of combustion reactions.

Related Questions


A 10-milliliter solution containing 2 grams of drug is a _______% solution.


Percentage by mass is the amount in mass of a component in a mixture per 100 unit of mass of the total mixture. Percentage by mass is the same as  %w/w. We can determine this by dividing the mass of the solute with the total mass of the mixture. From the problem statement, the mass of the component is given as 2 g and the mass of the total mixture is 10 milliliter. It would be difficult to express this in percent by mass since we do not have data in the density. We can only express this in percent by w/v which is grams per 100mL of solution.

%w/v = 2 g / 10mL x 100 = 20% w/v solution

What is the relationship between vapor pressure of a liquid and its boiling point?


If the intermolecular forces in a liquid are small, the molecules can easily escape from the surface of theliquid. The liquid will have a high vapour pressure. The normal boiling point is the temperature in which the vapour pressure of a liquid becomes equal to atmospheric pressure.

Which is the strongest reducing agent in the periodic table?


"Caesium" is the strongest reducing agent in Periodic table.

Hope this helps!
The strongest reducing agent in the periodic table is Carbon

Holding a marble at the top of a ramp is it a potential or kinetic


Potential because it is not moving yet

Potential, because it has the potential to have a large amount of kinetic energy.

Is calcium disodium ionic or covalent?


Calcium disodium is ionic. When you look at the periodic table, you can see that they are in the same group and that they re both metals. an ionic bond is formed by two or more nonmetals and a covalent bond is formed by two or more nonmetals.

How many neutrons does an atom of al-27 have? (hint: look at the periodic table for the atomic number aluminum (al) 13 14 27 40 aluminum has the atomic number of 13?


Yeah!! Atomic number of Aluminum  is 13

No. of neutrons = Mass number - atomic number

 27 - 13 =14

So, the number of neutrons in Al-17 is 14


Suppose that magnesium would react exactly the same as copper in this experiment. how many grams of magnesium would have been used in the reaction if 1.000 g of silver were produced? the atomic mass of magnesium is 24.31 g/mol, and the atomic mass of silver is 107.87 g/mol


The solution for this problem would be:

We are looking for the grams of magnesium that would have been used in the reaction if one gram of silver were created. The computation would be:

1 g Ag (1 mol Mg) (24.31 g/mol) / (2mol Ag)(107.87g/mol) = 0.1127 grams of Magnesium


The synthesis of methanol from carbon monoxide and hydrogen gas is described by the following chemical equation: CO(g)+2H2(g)?CH3OH(g)

The equilibrium constant for this reaction at 25 ?Cis Kc=2.3×104. In this tutorial, you will use the equilibrium-constant expression to find the concentration of methanol at equilibrium, given the concentration of the reactants.

The equilibrium-constant expression is a mathematical equation that can be rearranged to solve for any of the variables in it. Rearrange the equilibrium-constant expression to solve for [CH3OH].


Suppose that the molar concentrations for CO and H2 at equilibrium are [CO] = 0.02 M and [H2] = 0.06 M.

Use the formula you found in Part B to calculate the concentration of CH3OH.

Express your answer to one decimal place and include the appropriate units.



[CH3OH(g)] = 1.7 M


  • CO(g) + 2H2(g) ↔ CH3OH(g)

∴ Kc(25°C) = 2.3 E4 = [CH3OH(g)] / [CO(g)]×[H2(g)]²

⇒ [CH3OH(g)] = Kc.[CO(g)][H2(g)]²

∴ [CO(g)] = 0.02 M

∴ [H2(g)] = 0.06 M

⇒ [CH3OH(g)] = (2.3 E4)(0.02)(0.06)²

⇒ [CH3OH(g)] = 1.7 M


Atomic weight is equal to the number of protons and neutrons in the nucleus. atomic weight is equal to the number of protons and neutrons in the nucleus. a. True
b. False


Atomic weight is actually calculated by the sum of protons and neutrons of that atom. It is not equal to the number. You must add them for the result
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