Hi, I was just wondering how you would calculate how much gas would dissolve into 500ml of water and if there was 0.1% of the solute in the atmosphere in grams?
Am finding this very difficult!
Example: Hydrogen sulphide: molar mass: 34g/mol
Water: molar mass 34g/mol
To calculate how much gas would dissolve in a given volume of water, you can use Henry's Law. Henry's Law states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid.
To apply Henry's Law, you will need two pieces of information:
1. The Henry's Law constant (kH): This constant is specific to each gas and can be obtained from experimental data or reference tables.
2. The partial pressure of the gas: This is the fraction of the total atmospheric pressure that is contributed by the specific gas you are interested in. In this case, you mentioned that the solute has a concentration of 0.1% in the atmosphere.
Let's calculate the amount of hydrogen sulfide (H2S) dissolved in 500 ml of water.
Step 1: Convert the percentage of solute to a decimal:
0.1% = 0.1/100 = 0.001
Step 2: Calculate the partial pressure of the gas:
Partial pressure = total atmospheric pressure * fraction of the gas
Assuming atmospheric pressure is 1 atm, the partial pressure of H2S would be:
Partial pressure of H2S = 1 atm * 0.001 = 0.001 atm
Step 3: Look up the Henry's Law constant for H2S:
The Henry's Law constant for H2S is typically expressed as M/atm or mol/(L*atm). Let's assume the constant (kH) for H2S is 0.003 M/atm.
Step 4: Calculate the amount of H2S dissolved in the water:
Amount of H2S dissolved (in moles) = Henry's Law constant * partial pressure of H2S
Amount of H2S dissolved (in moles) = 0.003 M/atm * 0.001 atm = 0.000003 moles
Step 5: Convert moles to grams using the molar mass:
Amount of H2S dissolved (in grams) = Amount of H2S dissolved (in moles) * molar mass of H2S
Amount of H2S dissolved (in grams) = 0.000003 moles * 34 g/mol = 0.000102 grams
Therefore, approximately 0.000102 grams of hydrogen sulfide would dissolve in 500 ml of water, given a solute concentration of 0.1% in the atmosphere.
Remember to always check your units and make sure that they are consistent throughout the calculation.