Common Ion Effect and Ksp

[@torresthemonster]

Hi I am studying for the mcat, and this was a very good question. Thank you

[@OldSchoolChemistry]

Hey Torres, I am so glad. Good job working hard;)

[@abdullahkocalar1009]

very clear video thank you very much 🙏

[@OldSchoolChemistry]

Thank you Abdullah! I appreciate your comment:)

[@sharonblack8697]

Hello! great video by the way. I myself am very mathematically challenged, and was wondering if you could clarify on the at least two 0's apart rule? Thanks again!

[@OldSchoolChemistry]

Hi Sharon, sure! It is referring to the place holder. For example 0.01 and 0.0001 have 2 zeros different. You see this written in scientific notation at 1x10^-2 and 1x10^-4. You can look at the exponents in the scientific notation and see there are 2 zeros different (-2 compared to -4). I hope that helps! Thanks:)

[@sai-pq4rr]

i've looked to many explanation about common ion and i could definitely say that your videos about it are the best and made so much sense, but i have one question, why is ksp the same in pure water and with common ion also, i mean if we put common ion with a particular salt that has a particular ksp dosent that mean that the ksp of salt also change because the concentration has changed due to the common ion?

[@OldSchoolChemistry]

Hi Sai, thank you for your question. Equilibrium is the ratio of products over reactants. K always stays the same with a change of concentration or pressure. The system shifts forward or reverse to maintain the ratio of K. (A change in temperature actually changes the value, ratio, of K.). This all applies to Ksp. The amount of salt that will dissolve can be seen in the molarity of the ions. Even if there is a common ion, the molarity of ions from the salt will still be the same. It also helps to think that molarity is a ratio of moles of ions per liter of solution. For Ksp the Molarity of the ions/L remains the same at equilibrium. I hope that helps!