A 260-ml flask contains pure helium at a pressure of 756torr . A second flask with a volume of 470ml contains pure argon at a pressure of 717 torr .
A)If the two flasks are connected through a stopcock and the stopcock is opened, what is the partial pressure of helium?
B)If the two flasks are connected through a stopcock and the stopcock is opened, what is the partial pressure of argon?
C)If the two flasks are connected through a stopcock and the stopcock is opened, what is the total pressure?
To determine the answers, we need to apply Dalton's law of partial pressures. According to Dalton's law, the total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas.
A) To find the partial pressure of helium, we need to determine the moles of helium gas in the flask and calculate its partial pressure. We can use the ideal gas law equation, PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.
First, let's rearrange the equation to solve for n (number of moles): n = PV/RT.
Given:
Pressure of helium (P1) = 756 torr
Volume of helium flask (V1) = 260 ml
We need to convert the volume to liters and pressure to atmospheres to match the units of R (ideal gas constant). 1 atm = 760 torr.
1 atm = 760 torr
756 torr = 756/760 = 0.9947 atm
Converting volume from ml to L: 1 L = 1000 ml
260 ml = 260/1000 = 0.26 L
Standard temperature (T) = 273 K (assuming room temperature)
Using the ideal gas law equation: n1 = P1V1/RT
n1 = (0.9947 atm)(0.26 L) / (0.0821 L·atm/(mol·K))(273 K)
Simplifying the equation, we find that n1 = 0.0123 moles of helium.
Now, to determine the partial pressure of helium after the stopcock is opened, we need to consider the total moles of gas in both flasks. Since we know the volume and pressure of the argon flask, we can calculate the moles of argon (n2) using the same method.
Pressure of argon (P2) = 717 torr
Volume of argon flask (V2) = 470 ml = 0.47 L
Converting pressure to atm: 717 torr = 717/760 = 0.9421 atm
Using the ideal gas law equation: n2 = P2V2/RT
n2 = (0.9421 atm)(0.47 L) / (0.0821 L·atm/(mol·K))(273 K)
Simplifying the equation, we find that n2 = 0.0195 moles of argon.
B) The partial pressure of argon after the stopcock is open will be the same as its initial partial pressure since no argon molecules will escape or react during the process. Therefore, the partial pressure of argon will remain at 717 torr or 0.9421 atm.
C) The total pressure after the stopcock is opened will be the sum of the partial pressures of helium and argon. To calculate the total pressure, we add the partial pressures:
Total pressure = Partial pressure of helium + Partial pressure of argon
Total pressure = P1 + P2
Total pressure = 0.9947 atm + 0.9421 atm
Calculating the total pressure, we find that the total pressure is equal to 1.9368 atm.
PV = nRT. Calculate n for each flask.
a. moles He and PV = nRT calculates He partial pressure using total volume for V.
b. moles Ar and PV = nRT calculates Ar partial pressure using total volume for V.
c. total pressure is sum of partial pressures.