Ac sample of octane that has a mass of 0.750 g is burned in a bone calorimeter. As a result, the temperature if the calorimeter
2 answers:
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Answer:
80.92, Krypton
Explanation:
<u>What is effusion?</u>
• It is a process where gas escapes through a pinhole (a very small hole) into a region of low pressure or vacuum
<u>Graham's law of effusion of </u><u>gas</u>
• states that at a given constant temperature and pressure, the rate of effusion of gases is inversely proportional to the square root of their molar masses
<u>Calculations</u>
Nitrogen exist as N₂ at room temperature, thus its molar mass is 2(14)= 28.
Let the rate and molar mass of unknown gas be Rate₂ and M₂ respectively.
Since N₂ effuses 1.7 times as fast as the unknown gas,
Rate₁= 1.7(Rate₂)
Square both sides:
Multiply both sides by 28:
2.89(28)= M₂
M₂= 80.92
<u>Identity of </u><u>gas</u>
The molar mass of 80.92 lies between Bromine and Krypton. However since Bromine exist as Br₂, the value of it's molar mass would be 159.8 instead. Hence, Bromine is eliminated.
If the gas is a diatomic element, the atomic weight is 80.92 ÷2= 40.46. Thus, we are now considering if Argon could be its identity. However, Argon is a noble gas and will not exist as a diatomic element. Argon is therefore eliminated too.
Thus based on the above reasoning, its probable identity is Krypton.
Explanation:
As per the Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
Hence, according to this law the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
..........(1)
..............(2)
The final reaction is as follows:
.............(3)
Therefore, adding (1) and (2) we get the final equation (3) and value of at 298 K will be as follows.
=
+
= -314 kJ + (-80) kJ
= -394 kJ
Thus, we can conclude that at 298 K for the given process is -394 kJ.