The pH of a particular raindrop is 5.6. (b) What experiments could you do to test the hypothesis that the rain also contains sulfur-containing species that contribute to its pH? Assume you have a large sample of rain to test.

Video transcript

Hi everyone for this problem. It reads a water sample from a lake has a ph of 6.10. How can you test the hypothesis that dissolved carbon dioxide in the lake water contributes to its ph assume that the water sample is large enough to perform multiple test. Okay, so here we're looking for a hypothesis and we want to know how can we test the hypothesis that let's underline it dissolved carbon dioxide in the lake water contributes to its ph Okay, so, let's think about this. The presence of dissolved carbon dioxide contributes to the acidity of the lake water. So, we can write out an equation for this because when carbon dioxide dissolves in water, it produces something. Okay, And that equation is carbon dioxide plus water produces carbonic acid. Okay, so, this is one important equation we need to reference in terms of talking through this problem. Okay, so, carbon dioxide dissolves in water to produce carbonic acid. So, this carbonic acid here is a weak acid that can also react with water. And so let's go ahead and write out that reaction. So, we have carbonic acid and the state should be a gas here. Okay, so let's go ahead and erase that from here. So, this is a gas. Okay, so this is going to react with water and when it does, it produces hydro ni um or it dissociates into hydro ni um and bicarbonate ions. Okay, so, like we said, this, carbon this, yes, this carbonic acid is a weak acid, Okay, If carbon dioxide is somehow removed from the lake water. So, this carbon dioxide here, if it's somehow removed from the lake water, the amount of carbon or our amount of carbonic acid will decrease. Okay, they affect one another. And we can think about lash outliers principle when we think about this. Okay, When the amount of carbonic acid is decrease the amount of hydro ni um ions will also decrease. Alright. And this will decrease the acidity of the water sample and its ph would increase. Alright, so how can we remove carbon dioxide from the sample? We're dealing with gasses here. So the soluble itty of gasses is decreased when the temperature is increased. So if we heat the water sample, that's going to drive off the dissolved carbon dioxide gas and removal of the carbon dioxide gas from the sample will decrease the carbonic acid concentration and our first equation. And so the concentration of the hydro me um ions will decrease and that will decrease the acidity of the water sample. Okay, so in other words, what I'm saying is the ph of the sample will increase. And so what when when we're thinking about a hypothesis here, the hypothesis that can be tested is by heating the water sample to drive off the carbon dioxide and then testing the P. H. Again. Okay, so this is going to be our answer to this problem and that's it for our problem. I hope this was helpful