Student can predict the effect of pressure on gas solubility using Henry's Law.
Introduction to factors affecting gas solubility and dynamic equilibrium.
Many gases dissolve in water. While oxygen dissolves only to a small extent (just enough to sustain aquatic life), gases like hydrogen chloride (HCl) are highly soluble. The solubility of a gas is fundamentally driven by two external variables: temperature and pressure.
Visual of a piston increasing pressure over a solution.
As pressure increases, gas gets compressed into a smaller space, so more gas molecules strike the surface of the solution and dissolve—this is the basis of Henry’s law.
The partial pressure equation for Henry's Law.
Calculates millimoles of nitrogen dissolved in water.
Problem. If gas is bubbled through water at 293 K, how many millimoles of gas would dissolve in 1 litre of water? Assume that exerts a partial pressure of 0.987 bar. Given that Henry's law constant for at 293 K is 76.48 kbar.
Guided calculation of Henry's constant.
We are given the molality of as at STP, meaning moles of are dissolved in of water.
First, we calculate the number of moles of water in , which is .
Next, the mole fraction of () is calculated as the ratio , which gives approximately .
Henry's Law relates the partial pressure of the gas to its mole fraction in solution using the equation . At STP, assuming standard pressure , we rearrange the equation to solve for the constant.
Substituting the values gives , resulting in approximately .
Conceptual MCQ on Kh and temperature.
Why are aquatic species generally more comfortable in cold water than in warm water?
Calculates the quantity of CO2 in soda water.
Calculate the quantity of (in grams) in 500 mL of soda water when packed under 2.5 atm pressure at 298 K.
Given: Pa at 298 K. (Note: 1 atm = 101,325 Pa. Assume 500 mL of water = 500 g).
List the given variables and their values.
State Henry's Law.
Ensure pressure units match K_H before substituting.
Find the mole fraction, then relate it to the moles of CO2 (n).
Convert moles to grams (Molar mass of CO2 = 44 g/mol).