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Equilibrium and Le Chatelier (1 Viewer)
- Thread starter erucibon
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b) you need to think of what happens when you dissolve a non-metal oxide in water. In most cases dissolving non-metal oxide (i.e. a compound which has oxygen and a non-metal like SO2) produces an acidic solution (the only exceptions to this are: NO, N2O, CO for HSC purposes)
Adding CO2 (dry ice) causes the following reaction: CO2(g) + H2O(l) <---> H2CO3(aq)
This results in the production of carbonic acid, which can dissociate:
H2CO3(aq) <---> CO3^2- + 2H^+
As such because pH = -log[H^]+, increasing hydrogen ion concentration means pH decreases which explains why the pH changes from 10 to 4 (becoming more acidic because you have essentially added an acid)
c) So this is a really common question in equilibriums where the equilibrium equation contains a base and then you add an acid to it (or the other way around where if you had an acid component in the equilibrium and added a base to it). Recall here that what do acids like to react with --> bases and same thing if it was other way around
Adding the CO2 makes the carbonic acid, which reacts with the OH^- ions (H^+ + OH^- --> H2O). This is essentially the same as removing OH^- from the system, this will cause the equilibrium by Le chateliers principle to increase OH^- amount, (shifts equilibrium right). If you shift the equilibrium right more Fe(SCN)^2+ is also made which makes the solution go red
The whole trick with this type of question is understanding which part of the reaction does the component added react with. Commonly you would have already seen questions like predict what happens to the equilibrium if I remove hydroxide ions. This is identical to that but gets you thinking more in terms of how were those hydroxide ions actually removed. In this case they are removed via a chemical reaction
Other examples of that kind of thing where they imply removal of something without explicitly using the words include:
N2(g) + 3H2(g) <--> 2NH3(g)
where here they will say we liquefied ammonia. Liqueifying ammonia making it into a liquid removes [NH3(g)] concentration which shifts equilibrium right
Adding CO2 (dry ice) causes the following reaction: CO2(g) + H2O(l) <---> H2CO3(aq)
This results in the production of carbonic acid, which can dissociate:
H2CO3(aq) <---> CO3^2- + 2H^+
As such because pH = -log[H^]+, increasing hydrogen ion concentration means pH decreases which explains why the pH changes from 10 to 4 (becoming more acidic because you have essentially added an acid)
c) So this is a really common question in equilibriums where the equilibrium equation contains a base and then you add an acid to it (or the other way around where if you had an acid component in the equilibrium and added a base to it). Recall here that what do acids like to react with --> bases and same thing if it was other way around
Adding the CO2 makes the carbonic acid, which reacts with the OH^- ions (H^+ + OH^- --> H2O). This is essentially the same as removing OH^- from the system, this will cause the equilibrium by Le chateliers principle to increase OH^- amount, (shifts equilibrium right). If you shift the equilibrium right more Fe(SCN)^2+ is also made which makes the solution go red
The whole trick with this type of question is understanding which part of the reaction does the component added react with. Commonly you would have already seen questions like predict what happens to the equilibrium if I remove hydroxide ions. This is identical to that but gets you thinking more in terms of how were those hydroxide ions actually removed. In this case they are removed via a chemical reaction
Other examples of that kind of thing where they imply removal of something without explicitly using the words include:
N2(g) + 3H2(g) <--> 2NH3(g)
where here they will say we liquefied ammonia. Liqueifying ammonia making it into a liquid removes [NH3(g)] concentration which shifts equilibrium right
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