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Chemistry Homework Help => AP Chemistry => Topic started by: Aditi on April 29, 2024, 12:54:09 AM

Title: net ionic rection ,ion concentrations. Limiting reactant and amount of solid formed
Post by: Aditi on April 29, 2024, 12:54:09 AM
15.0 ml of 0.250 M potassium iodide is mixed with 40 ml of  0.170 M silver chromate.

Please write Molecular, total, and ionic equations.

set up the BCA table.
Calculate the concentrations of all ions after the reaction
Title: Re: net ionic concentrations
Post by: Aditi on April 29, 2024, 12:58:32 AM
need the limiting reactant as well. thank you
Title: Re: net ionic concentrations
Post by: Aditi on April 29, 2024, 01:00:53 AM
How many grams of precipitate will form?
Title: Re: net ionic concentrations
Post by: uma on April 29, 2024, 02:26:05 AM
Quote from: Aditi on April 29, 2024, 12:54:09 AM15.0 ml of 0.250 M potassium iodide is mixed with 40 ml of  0.170 M silver chromate.

Please write Molecular, total, and ionic equations.
 
Balanced molecular equation is :
2KI(aq) + Ag2CrO4  -> K2CrO4 (aq) + 2AgI(s)

Now from solubility rules we know-
All K+ and all CrO42- ions containing compounds are strong electrolytes and  AgI is not so soluble.
 2K+(aq) + 2I-(aq) + 2Ag+ (aq) + CrO4 2- (aq) ->2AgI(s) +2K+(aq) + CrO4 2- (aq)
Spectator ions are
CrO4 2- (aq) and K+(aq)
Cancel them and net ionic equation is
2I-(aq) + 2Ag+ (aq) -> 2AgI(s)
Title: Re: net ionic concentrations in reactions
Post by: uma on April 29, 2024, 02:47:05 AM
Quote from: Aditi on April 29, 2024, 12:54:09 AM15.0 ml of 0.250 M potassium iodide is mixed with 40 ml of  0.170 M silver chromate.
 
set up the BCA table.
Calculate the concentrations of all ions after the reaction
15.0 ml of 0.250 M potassium iodide 
Moles of KI = moles of I- = M * V (L) = 3.75* 10^-3 mol  = moles of K+
40 ml of  0.170 M silver chromate.
Moles of Ag2CrO4  = 2moles of Ag+ = M * V(L) = 6.8 * 10^-3 mol = moles of CrO4 2-
Moles of Ag+ = 6.8 * 10^-3 mol= 3.4*10^-3 mol

                    I-(aq)    +        Ag+ (aq)  ->          AgI(s)
B                  3.75* 10^-3          3.4*10^-3                  0
C                  -3.4*10^-3          -3.4*10^-3              +3.4*10^-3
A                  0.35 *10^-3            0                    3.4*10^-3
Only I- and Spectator ions CrO4 2- (aq) and K+(aq)
are  left in the solutions.
Total volume of the solution = 15.0 + 14.0 = 29.0 mL
[I-] = 0.35 *10^-3  / 29.0
[K+] = 3.75* 10^-3  /  29.0
Title: Limiting reactant
Post by: uma on April 29, 2024, 02:49:23 AM
Quote from: Aditi on April 29, 2024, 12:58:32 AMneed the limiting reactant as well. thank you
Limiting reactant is the one which gets completely used up or the one which gives minimum amount of the product.
Check BCA and check finally which reactant is used up completely.
Title: Re: net ionic rection ,ion concentrations. Limiting reactant and amount of solid formed
Post by: uma on April 29, 2024, 02:53:06 AM
Quote from: Aditi on April 29, 2024, 01:00:53 AMHow many grams of precipitate will form?
Solid formed is AgI.
Get the moles of AgI from BCA table and convert that it into grams.
We know moles = mass / molar mass
Rearrange the above equation
mass = moles * molar mass
Title: Re: net ionic rection ,ion concentrations. Limiting reactant and amount of solid formed
Post by: Aditi on April 29, 2024, 11:53:33 AM
thank you