The hydrogen gas is collected over water at 25.0°c. The volume of the gas is 246 ml measured at 760 mmhg. calculate the number of grams of h2 collected (vapor pressure of h2=23.76mmhg)
To calculate the number of grams of H2 collected, we need to correct for the vapor pressure of water at the given temperature since the hydrogen gas is collected over water.
To start, we need to find the pressure of H2 gas alone, excluding the vapor pressure of water. We subtract the vapor pressure of water at 25.0°C (which is 23.76 mmHg) from the total pressure of the gas collected.
Partial pressure of H2 gas = Total pressure - Vapor pressure of water
Partial pressure of H2 gas = 760 mmHg - 23.76 mmHg
Partial pressure of H2 gas = 736.24 mmHg
Now we need to convert the volume of the gas collected to liters. There are 1000 mL in 1 L, so:
Volume of H2 gas = 246 mL = 246/1000 L = 0.246 L
Next, we can use the ideal gas equation to calculate the number of moles of H2 gas. The ideal gas equation is:
PV = nRT
Where:
P = pressure of gas (in atm)
V = volume of gas (in L)
n = number of moles of gas
R = ideal gas constant (0.0821 L.atm/mol.K)
T = temperature (in Kelvin)
First, let's convert the pressure from mmHg to atm:
Partial pressure of H2 gas = 736.24 mmHg * (1 atm/760 mmHg) = 0.968 atm
Now we substitute the known values into the ideal gas equation:
(0.968 atm) * (0.246 L) = n * (0.0821 L.atm/mol.K) * (25.0 + 273.15 K)
Simplifying the equation:
0.238608 = n * (20.88)
Now solve for the number of moles of H2 gas:
n = 0.238608 / 20.88
n = 0.01144 moles
Finally, to calculate the mass (in grams) of H2 gas collected, we need to use the molar mass of hydrogen, which is 2.02 g/mol:
Mass of H2 gas = Number of moles * Molar mass
Mass of H2 gas = 0.01144 moles * 2.02 g/mol
Mass of H2 gas = 0.0231208 g
Therefore, the number of grams of H2 gas collected is approximately 0.0231 grams.