A sample of hydrogen gas was collected over water at 36 degrees celsius and 855 mmHg. The volume of the container was 6.50 L. Calculate the number of moles of H2 collected. (vapor pressure of water is 44.6 torr at 36 degrees Celsius)

Use PV = nRT

A gas was collected over water in a system at 30 degees celsius. If atmospheric pressure was measured at 758.8 mmHg, what was the pressure of the collected gas?

To find the number of moles of hydrogen gas collected, we need to use the ideal gas law equation:

PV = nRT

Where:
P = Pressure (in atm)
V = Volume (in liters)
n = Number of moles
R = Ideal Gas Law constant (0.0821 L·atm/mol·K)
T = Temperature (in Kelvin)

First, let's convert the given pressure from mmHg to atm:
855 mmHg = 855/760 atm ≈ 1.125 atm

Next, let's convert the temperature from degrees Celsius to Kelvin:
T = 36°C + 273.15 = 309.15 K

Now we can substitute the given values into the ideal gas law equation and solve for n:

(1.125 atm)(6.50 L) = n(0.0821 L·atm/mol·K)(309.15 K)

Multiply the values on the left side of the equation:
7.3125 = n(0.0821)(309.15)

Divide both sides of the equation by (0.0821)(309.15):
n = 7.3125 / (0.0821)(309.15)

Calculating this expression will give you the number of moles of hydrogen gas collected.

To calculate the number of moles of hydrogen gas collected, we can use the ideal gas law equation:

PV = nRT

Where:
P = pressure of the gas (in atm)
V = volume of the gas (in liters)
n = number of moles of the gas
R = the ideal gas constant (0.0821 atm·L/mol·K)
T = temperature of the gas (in Kelvin)

First, let's convert the given conditions to the appropriate units:

Given:
Temperature (T) = 36 degrees Celsius
Pressure (P) = 855 mmHg
Volume (V) = 6.50 L
Vapor Pressure of water at 36 degrees Celsius = 44.6 torr

Step 1: Convert temperature to Kelvin
To convert Celsius to Kelvin, we use the equation:
T(K) = T(C) + 273.15

T(K) = 36 + 273.15
T(K) = 309.15 K

Step 2: Convert pressure to atm
Since the ideal gas law requires pressure to be in atm, we need to convert mmHg to atm.
1 atm = 760 mmHg

P(atm) = P(mmHg) / 760

P(atm) = 855 mmHg / 760
P(atm) = 1.125 atm

Step 3: Calculate the partial pressure of hydrogen gas
Since the gas was collected over water, we need to subtract the vapor pressure of water from the total pressure to find the partial pressure of the hydrogen gas.

Partial pressure of H2 = Total pressure - Vapor pressure of water

Partial pressure of H2 = 1.125 atm - 0.0588 atm (converted from 44.6 torr using P(atm) = P(torr) / 760)
Partial pressure of H2 = 1.0662 atm

Step 4: Calculate the number of moles
Now we can rearrange the ideal gas law equation to solve for the number of moles (n):

n = PV / RT

n = (1.0662 atm × 6.50 L) / (0.0821 atm·L/mol·K × 309.15 K)
n ≈ 0.267 moles

Therefore, the number of moles of hydrogen gas collected is approximately 0.267 moles.