Anonymous
Anonymous asked in Science & MathematicsChemistry · 9 years ago

# CHEMISTRY QUESTION~~~~~~?

When a 52cm^3 flask is filled with a gas at 200 degree celcius, the pressure produced is 1.29 X 10^5Pa. If the temperature is then increased to 400 degree celcius, the pressure increases to 3.68 X 10^5 Pa. Which statement explains these observations?

(A) The gas obeys Boyle's law.

(B) The gas exists as a dimer at 200 degree celcius.

(C) The number of gas molecules increases by 2.85 times at 400 degree celcius.

(D) The number of collisions between gas molecules and the wall of the flask doubles at 400 degree celcius.

Can u explain it? thx..

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• 9 years ago

Boyle's Law states that the Pressure of a gas is inversely proportional to the Volume of that gas, as long as Temperature is kept constant. If this experiment temperature is not constant so it is not answer A.

For D, the number of collision with the walls of the container is directly proportional to the pressure on the container. As at 200 C the pressure isn't half what it is at 400 C then this can't be true either (The main reason this statement isn't true is that you are working in degrees Celsius when gas laws have to be in kelvin. So a jump from 200K to 400K would give twice the number of collisions).

Answers B and C are closely linked. There is an equation which states pV = nRT where p is pressure in pascals, V is volume in m^3, n is number of moles of gas, R is a constant 8.31, and T is temperature in Kelvin. pV/TR gives n the number of moles. In the first scenario, doing this calculation, you get this as:

(52 x 10^-6 * 1.29*10^-5) / (8.31 * 473) = 0.0017

In the second scenario, doing the same thing, you get 0.0034

This means the number of moles have doubled so it rules out answer C as the number of molecules is directly proportional to the number of moles.

Therefore, either by process of elimination, or by the fact that at 200C it was a dimer molecule and then above that it split into its singular molecules, thus doubling the number of molecules and the number of moles, the correct answer is B

Source(s): I'm a nerd :D