Solving Equilibrium Question: Calculate Acetate Ion Concentration

[Jules18]

Hey guys, I've tried this question a couple different ways. Please help!

Homework Statement

Calculate the concentration of the acetate ion (M) in a solution prepared by dissolving 1.00×10-3 mol of HCl(g) in 1.00 L of 1.90 M aqueous acetic acid. Ka = 1.7E-5

And at that point I'm not sure what to do.

Homework Equations

... CH3COOH --> CH3COO- + H+
initial: 1.90 M 0 0
change: - x +x +x
equlbm: ~1.9 x x

The Attempt at a Solution

I did some calculations and found that x = 5.68E-3 . I that didn't take the HCl into consideration, though - I really have no idea what to do with that. i

 

[Borek]

As you were already told at CF - concentration of H⁺ should account for the HCl. It is fully dissociated.

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[Blueshift5]

'm not sure how the HCl would affect the equilibrium.

I would first start by identifying the relevant equations and variables for this problem. In this case, the relevant equations are the equilibrium constant (Ka) and the dissociation of acetic acid into acetate ion and hydrogen ions. The variables we are given are the initial concentration of acetic acid (1.90 M) and the amount of HCl added (1.00×10-3 mol).

Next, I would use the equation for the dissociation of acetic acid to set up an equilibrium expression and solve for the concentration of acetate ion (x). We can ignore the HCl since it is a strong acid and will dissociate completely, meaning it will not have an effect on the equilibrium.

Based on the calculations provided, it appears that the student has correctly identified the change and equilibrium concentrations for acetic acid, acetate ion, and hydrogen ions. However, the value of x calculated does not take into account the initial concentration of acetic acid. To calculate the concentration of acetate ion, we need to add the initial concentration of acetic acid (1.90 M) to the value of x.

Once we have the value of x, we can use it to calculate the concentration of acetate ion by dividing it by the total volume of the solution (1.00 L). This will give us the final concentration of acetate ion in units of M.

In summary, to solve this equilibrium question, we need to set up an equilibrium expression, account for the initial concentration of acetic acid, and use the value of x to calculate the concentration of acetate ion. This is a common type of problem in chemistry and it is important to carefully consider all the relevant equations and variables in order to arrive at the correct solution. I hope this helps!