The TSR Community Awards 2025 are now live >>

GCSE chemistry question help

Hi. Pls can someone help me with this question. I now know the answer is B but I don’t know how. Thank you!
4F987DF3-6B3A-4A51-A23E-E7A346C05AB7.jpg.jpeg

Reply 1

moffs

Original post

by Mickey Mouse 1

Hi. Pls can someone help me with this question. I now know the answer is B but I don’t know how. Thank you! 4F987DF3-6B3A-4A51-A23E-E7A346C05AB7.jpg.jpeg

I could be wrong and may not explain this very well but I'll try my best

The pale blue solution is a solution made up of a unknown substance, say x, + water + copper ions

When the chloride ions (a pure substance that therefore can't be broken down further) is added, it binds to some of the atoms/molecules in the blue solution leaving two products; water and a new, yellow, solution

From rearranging we can see this solution must be made up of x, copper ions, and chloride ions
Due to the reaction taking place these will no longer be ions and gain full outer shells

When removing the chloride ions, the copper returns to it's ionic form and thus binds with the water again to regain its full/stable outer shell

Hope I explained it in a way that Kind of made sense
Hope this helps :smile:

Edit: a possibly simpler explanation-
All atoms try to achieve the most stable form possible
This includes gaining a full outer shell of electrons and this is why ions tend to bind to others to achieve this state
When adding the chloride ions, the ions in the solution are more stable when bound to chloride ions and so choose to do so leaving the hydrogen and oxygen atoms to form water
When the chloride ions are taken away again their most stable option is to return to their original form (the blue solution)

Hopefully this makes more sense :smile:

(edited 1 year ago)

Reply 2

Mickey Mouse 1

Thank you!! Your explanation really helped :smile:

Reply 3

moffs

Original post

by Mickey Mouse 1

Thank you!! Your explanation really helped :smile:

I'm very happy to hear it and glad to help :smile:

Reply 4

Mstew!

I think it’s an equilibrium question, so the gcse way to think about it is that removing chloride ions decreases the chloride concentration, disturbing the equilibrium—-> this means the equilibrium positions shifts to oppose this change by moving to the left to produce more chloride ions and restore the equilibrium constant (don’t need to know about constant for gcse). If the equilibrium has shifted to the left, then more blue solution will be produced along with more chloride ions, so the reaction mixture becomes more blue overall