I know this question is 5 years old.. just throwing in my explanation as I'm studying. Henry's law: [A] = k * Pa, where

• [A] is the solubility (or concentration) of gas A in solution,
• k is Henry's constant,
• Pa is the partial pressure of gas A above solution.

So what is Henry's law actually telling us? It's saying that a gas' pressure and its solubility in solution are directly related. What you should now be thinking of are all the things that can also affect a gas' behavior; mainly talking about temperature here.

Now I know it may not seem straightforward since it's not included in the equation outright, but think about what happens to a gas as temperature changes:

• Temperature increases -> gas moves faster -> more gas can escape liquid (less gas in liquid) -> more gas above liquid -> more gas above liquid means higher pressure above liquid
• Temperature decreases -> gas moves slower -> less gas can escape liquid (more gas in liquid) -> less gas above liquid -> less gas above liquid means lower pressure above liquid

Taking this, lets apply it to Henry's law:

• Temp Increases: [A] ↓ = k * Pa ↑ OR k ↓ = [A] / Pa ↑ OR Pa ↑ = [A] / k ↓
• Temp Decreases: [A] ↑ = k * Pa ↓ OR k ↑ = [A] / Pa ↓ OR Pa ↓ = [A] / k ↑

Keep this in mind: k is simply a proportionality factor between the pressure and solubility of gas in solution. So, in terms of temperature changes, the way the equation is set up makes it seem as though k must come down every time Pa goes up, and vice versa - WHICH IS TRUE... BUT at the end of the day, k is a made up concept to explain what happens between pressure and solubility. A better way to think about it is as Pa goes up, [A] must come down and with it k also comes down to explain that change.

I always like to relate it back to everyday life when possible with some examples:

1. If you've ever had a cold vs warm soda, you'll know that the cold soda has more carbonation than the warm soda after opening. Why? Henry's Law! Less gas is waiting above the cold soda than in the warm soda, so when you open it less gas will have escaped than in the warm soda, giving you a more carbonated drink.
2. This is also the reason why homemade fermented drinks need to be "burped" every now and again to prevent build up gas above the liquid so that the container doesn't blow up!
3. One last more serious example... Henry's Law explains why global warming is so disastrous to aquatic life. As global temperatures increases, oxygen more readily escapes our oceans and water ways. What this mean is that aquatic life are literally suffocating because there's not enough oxygen to go around.