146 mL of wet H2 gas is collected over water at 29.0 degrees celsius and room pressure of 750 torr. give the volume of the dry H2 gas collected at STP, give the mass of the dry H2 collected, and give the volume of the dry H2 at room conditions and the volume of H2O in the collected gas at room conditions.

could someone please please pleasee help me? i'm soo confused >.< i don't understand the whole wet/dry thingy at alllll.

http://www.jiskha.com/display.cgi?id=1291861416

Of course! I'd be happy to help you understand the concept of wet and dry gases and guide you through solving this problem.

When we say a gas is "wet," it means that it contains some water vapor, while a "dry" gas does not contain any water vapor. In this problem, we have a wet gas (H2) collected over water, and we need to find the volume of the dry gas, as well as the mass of the dry H2 collected. Let's break the problem down step by step!

Step 1: Convert the temperature to Kelvin
The temperature is currently given in degrees Celsius, but we need to work with the Kelvin scale for gas calculations. To convert from Celsius to Kelvin, you simply add 273.15 to the given temperature. In this case, 29.0 degrees Celsius becomes 29.0 + 273.15 = 302.15 K.

Step 2: Convert the pressure to atmospheres
The pressure is currently given in torr, but we typically work with the SI unit of pressure, which is the atmosphere (atm). To convert pressure from torr to atm, we divide by 760 (since 1 atm = 760 torr). In this case, 750 torr becomes 750 / 760 = 0.9868 atm.

Step 3: Apply Dalton's Law of Partial Pressures
Dalton's Law states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases. In our case, the wet H2 gas collected over water has a total pressure of 0.9868 atm.

Step 4: Apply the ideal gas law to solve for the volume of dry H2 at STP
The ideal gas law is given by the equation PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant (0.0821 L.atm/mol.K), and T is the temperature in Kelvin.

Since we want to find the volume of the dry H2 gas at STP (standard temperature and pressure), we can rearrange the ideal gas law equation to solve for V:

V = (nRT) / P

At STP, the pressure is 1 atm, and the temperature is 273.15 K. We need to calculate the number of moles of H2 gas using the given information.

Step 5: Calculate the number of moles of wet H2 gas
To calculate the number of moles of H2 gas collected, we need to use the concept of partial pressure. Since the total pressure of the collected gas is 0.9868 atm, and the pressure due to water vapor is the vapor pressure of water at the given temperature, we can subtract the vapor pressure from the total pressure to get the partial pressure of H2 gas.

At 29.0 degrees Celsius, the vapor pressure of water is 30 torr. Therefore, the partial pressure of H2 gas is 750 torr - 30 torr = 720 torr (which is equivalent to 0.947 atm).

To calculate the number of moles of H2 gas, we can use the ideal gas law equation:

PV = nRT

n = (PV) / RT

n = (0.947 atm * 0.146 L) / (0.0821 L.atm/mol.K * 302.15 K)

Calculate n using the above formula.

Step 6: Calculate the volume of dry H2 gas at STP
Now that we know the number of moles of wet H2 gas, we can substitute it into the equation for V at STP:

V = (nRT) / P

V = [(number of moles of wet H2 gas * 0.0821 L.atm/mol.K * 273.15 K) / (1 atm)]

Calculate V using the above formula.

Step 7: Calculate the mass of the dry H2 gas
To find the mass of the dry H2 gas collected, we need to use the molar mass of hydrogen, which is approximately 2.016 grams per mole. Multiply the number of moles of H2 gas (from Step 5) by the molar mass of H2 to get the mass in grams.

Step 8: Calculate the volume of the dry H2 gas at room conditions
To find the volume of the dry H2 gas at room conditions, we already have the volume at STP (from Step 6). Since we know the relationship between volume and temperature for gases (assuming the pressure is constant), we can use the equation:

(V2 / V1) = (T2 / T1)

Substitute the given temperature and the volume at STP to find the volume at room conditions.

Step 9: Calculate the volume of H2O in the collected gas at room conditions
To find the volume of water vapor in the collected gas at room conditions, we can subtract the volume of dry H2 gas (from Step 8) from the total volume of the collected gas (146 mL) at room conditions. This difference will give us the volume of H2O in the gas.

I hope this step-by-step guide helps you understand how to tackle this problem. Let me know if you have any further questions!