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Chemical reactions HELP (1 Viewer)
- Thread starter saraahhpp
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- #chemistry
This type of question tests solubility rules as well as some other things that you see when a chemical reaction
When it says no visible reaction this does not mean a reaction has not occurred, it just means we can’t tell if it did or not because we don’t have a physical indication like a precipitate, colour change or gas being made
When trying to solve this type of question, because the no visible reaction results don’t tell you as much information. You want to focus on the results that stick out I.e gas produced or precipitate made
Okay so starting with the bubbles observed result. This indicates a gas was made when hcl was added to the sample.
There are only really two reactions that make gases with acid reactions these are: co2 when the compound contains carbonate ions and h2 when acid is reacted with a metal
As we don’t have a neutral metal in our case,
We only focus on the carbonate reaction
When justifying your answer you want to always provide a chemical reaction if what you said is a reaction between something happened
2Hcl+co3 2- —-> co2 + h2o + 2cl- (don’t forget to add states)
Because we have gas being made when acid is added our anion is carbonate
Now look at the result with agno3 being added making a precipitate. You will have to have a knowledge of precipitate rules for this (many videos on YouTube that give ways to remember them)
Silver ions form precipitates with sulfate ions, carbonate ions, hydroxide ions and phosphate ions
This doesn’t really help us much because we already know the sample has carbonate
So now we use the more ambiguous no visible reaction results
Basically for this just need to have reactions that do NOT make precipitates
If you combine the choices of cations we have with the remaining NaOH and Na2SO4. Ca2+ would make a precipitate with both the solutions
Cu2+ would make a precipitate with naoh but not with na2so4
Will na+ makes no precipitates so as we got no visible reaction in both only possibility is na+
(once again precipitate rules for the above)
So that means we have na+ and co3 2- in our solution
When it says no visible reaction this does not mean a reaction has not occurred, it just means we can’t tell if it did or not because we don’t have a physical indication like a precipitate, colour change or gas being made
When trying to solve this type of question, because the no visible reaction results don’t tell you as much information. You want to focus on the results that stick out I.e gas produced or precipitate made
Okay so starting with the bubbles observed result. This indicates a gas was made when hcl was added to the sample.
There are only really two reactions that make gases with acid reactions these are: co2 when the compound contains carbonate ions and h2 when acid is reacted with a metal
As we don’t have a neutral metal in our case,
We only focus on the carbonate reaction
When justifying your answer you want to always provide a chemical reaction if what you said is a reaction between something happened
2Hcl+co3 2- —-> co2 + h2o + 2cl- (don’t forget to add states)
Because we have gas being made when acid is added our anion is carbonate
Now look at the result with agno3 being added making a precipitate. You will have to have a knowledge of precipitate rules for this (many videos on YouTube that give ways to remember them)
Silver ions form precipitates with sulfate ions, carbonate ions, hydroxide ions and phosphate ions
This doesn’t really help us much because we already know the sample has carbonate
So now we use the more ambiguous no visible reaction results
Basically for this just need to have reactions that do NOT make precipitates
If you combine the choices of cations we have with the remaining NaOH and Na2SO4. Ca2+ would make a precipitate with both the solutions
Cu2+ would make a precipitate with naoh but not with na2so4
Will na+ makes no precipitates so as we got no visible reaction in both only possibility is na+
(once again precipitate rules for the above)
So that means we have na+ and co3 2- in our solution