If 4.0 grams of hydroven, 6.02 x 10^22 atoms of helium and 4.48 liters of argon, measured at STP are placed in a 2.0 liter flask, at 27 degrees C, what is the final pressure?
Under controlled conditions the velocity of hydrogen molecules was found to be 250 meters/sec, and the velocity of an unknown gas was found to be 88.4 meters/sec. What is the molecular weight of the unknown gas?
convert 4 g hydrogen to moles.
Convert 6.02 x 10^22 atoms He to moles.
Convert 4.48 L Ar to moles.
Add all the moles together and use PV - nRT to solve for pressure.
but how do u convert L to moles?
It is at STP, so use 22.4 L per mole
To find the final pressure in the first question, we can use the ideal gas law equation: PV = nRT.
First, let's calculate the number of moles for each gas:
1. Hydrogen (H2) has a molar mass of 2.02 g/mol. Given 4.0 g of hydrogen, we can calculate the number of moles using the formula:
Number of moles = mass / molar mass
Number of moles of hydrogen = 4.0 g / 2.02 g/mol
2. For helium (He), we are given the number of atoms, so we need to convert the number of atoms to moles. With Avogadro's number (6.02 x 10^23 atoms/mol), we can calculate the number of moles:
Number of moles of helium = (6.02 x 10^22 atoms) / (6.02 x 10^23 atoms/mol)
3. For argon (Ar), we are given the volume at STP (Standard Temperature and Pressure), so we can use the ideal gas law rearranged to solve for moles:
Number of moles of argon = (PV) / (RT)
Assuming the temperature is given in Celsius, you need to convert it to Kelvin by adding 273.
Number of moles of argon = (1 atm x 4.48 L) / (0.0821 atm·L/mol·K x (27°C + 273))
Once you have the number of moles for each gas, you can sum them up to find the total number of moles. Divide this by the final volume (2.0 L) to find the final pressure using the ideal gas law equation (PV = nRT). Remember to convert the temperature to Kelvin as well.
For the second question, we can use the average kinetic energy of gas molecules to calculate the molecular weight of the unknown gas.
The average kinetic energy of a gas is given by the equation:
Average kinetic energy = (3/2) x (k) x (temperature)
Since the average kinetic energy is directly proportional to the square of the velocity, we can compare the unknown gas's average kinetic energy to hydrogen's average kinetic energy:
(Velocity of unknown gas)^2 / (Velocity of hydrogen)^2 = (Molar mass of hydrogen) / (Molar mass of unknown gas)
Rearranging the equation, we can solve for the molecular weight of the unknown gas:
Molecular weight of unknown gas = (Molar mass of hydrogen) x (Velocity of unknown gas)^2 / (Velocity of hydrogen)^2
Plug in the given values for the velocity of hydrogen (250 m/s) and the velocity of the unknown gas (88.4 m/s) to calculate the molecular weight of the unknown gas.