Answer: C. ethanol
The enthalpy of combustion is the amount of heat produced when one mole of ethanol undergoes complete combustion at 25 ° C and 1 atmosphere pressure, yielding products also at 25 ° C and 1 atm.
<u>The enthalpy of combustion of the unknown compound is</u>
ΔH = - 320 kJ / 0.25 mol = - 1280 kJ / mol
<u>To choose a probable compound according to this combustion enthalpy, we must evaluate the deviation in relation to the values reported in the literature for the three probable compounds</u> (methane, ethylene and ethanol). The deviation (e%) will be calculated according to the following equation,
e% = ( | ΔHx - ΔH | / ΔHx ) x 100%
where ΔHx is the enthalpy of combustion of the probable compound.
The following table shows the combustion enthalpies of the probable compounds and their deviation in relation to the enthalpy of ΔH = - 1280 kJ / mol
Compound Enthalpy of combustion (kJ/mol) Deviation
Methane - 890.7 43.8%
Ehylene -1411.2 9.3%
Ethanol -1368.6 6.5%
According to the previous table, we can say that the most probable compound is ethanol, since it has the smallest deviation in relation to the experimental enthalpy value of combustion.
Answer:
Explanation:
The given reaction equation is:
2A + 4B → C + 3D
We know the mass of compound A in the reaction above. We are to find the mass of compound D.
We simply work from the known mass to calculate the mass of the unkown compound D
Using the mole concept, we can find the unknown mass.
Procedures
- We first find the molar mass of the compound A from the atomic units of the constituent elements.
- We then use the molar mass of A to calculate its number of moles using the expression below:
Number of moles of A = 
- Using the known number of moles of A, we can work out the number of moles of D.
From the balanced equation of the reaction, it is shown that:
2 moles of compound A was used up to produced 3 moles of D
Then 
x number of moles of A would give the number of moles of D
- Now that we know the number of moles of D, we can find its mass using the expression below:
Mass of D = number of moles of D x molar mass of D
<span>The average speed of the gas is related to the kinetic
energy of the gas. The kinetic energy of
the gas is also related to the temperature of the gas. If the average speed of
the gas is closer to zero, it means that it has very low motion or kinetic
energy. This can be inferred that the gas has a very low temperature. At absolute
zero, the motion of all the gas molecules stops. This means that the kinetic
energy of the gas is also zero. Zero kinetic energy means zero average speed.</span>
<span>So, the answer is cylinder B. The average speed of the gas
in cylinder B is closest to zero.</span>
Explanation:
when an iron bar rust is an example of a chemical change in which a new substance is formed and the change is not easily reversible.for iron to rust moisture and air must be present.while when a substance freezes,it can be easily reversed through melting and no new substance is formed.this change is termed a physical change.
