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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Win,odd Dhamnekar on June 10, 2021, 10:52:26 AM

Title: Prediction of precipitation
Post by: Win,odd Dhamnekar on June 10, 2021, 10:52:26 AM
In all the following exercises M represents metal and X represents anion.


a) The salt, MX2 has a Ksp of 2.00e-6. If equal volumes of 0.0059M M(NO3)2 and 0.01M NaX are mixed, will solid form?

b)The salt, MX3 has a Ksp of 2.07e-10. If equal volumes of 0.0029M M(NO3)3 and 0.02M NaX are mixed, will solid form?

c)The salt, MX has a Ksp of 2.13e-6. If equal volumes of 0.0062M M(NO3)2 and 0.03M Na2X are mixed, will solid form?

My worked out answers:

a)Qion=0.00295*0.012=2.95e-7 which is less than the given Ksp 2.00e-6, hence solid won't form.

b)Qion=0.00145*(0.03)3=3.915e-8 which is greater than the given Ksp 2.07e-10, hence, solid will form.

c)Qion=0.0031*0.015= 465e-5 which is greater than the given Ksp 2.13e-6, hence solid will form.

What is your opinion about these answers? Are these answer correct? In my opinion, all  these three answers are correct.
Title: Re: Prediction of precipitation
Post by: mjc123 on June 10, 2021, 04:35:08 PM
Where do you get the value 0.03 in b? Or 0.01 in a?
Title: Re: Prediction of precipitation
Post by: Win,odd Dhamnekar on June 11, 2021, 02:12:23 AM
In b) , Initial concentration of salt MX3 is 0.02M.After mixing equal volumes of metal(M) and anion(X), it will be 0.01. Then it will be multiplied by X's subscript in MX3=0.03.

Similar is the case for (a).
Title: Re: Prediction of precipitation
Post by: mjc123 on June 12, 2021, 01:51:19 PM
You don't have MX3, you have M(NO3)3 and NaX. After mixing, you have 0.00145 M M3+ and 0.01 M X-.

You mustn't assume there are stiochiometric  amounts of M and X!