Asked by Molly B
                If the Ka of a monoprotic weak acid  is 4.5x10^-6 what is the pH of a .10M solution of this acid.
I don't even know how to start this problem, I'm totally lost please help!
            
        I don't even know how to start this problem, I'm totally lost please help!
Answers
                    Answered by
            DrBob222
            
    Step 1. Write and balance the equation.
Step 2. Complete the ICE chart (initial, change. equilibrium).
Step 3. Write the Ka expression.
Step 4. Substitute the E line of the ICE chart into Ka expression and solve for the unknown.
.........HA ==> H^+ + A^-
I........0.1....0......0
C........-x.....x......x
E......0.1-x....x......x
Ka = (H^+)(A^-)/(HA)
4.5E-6 = (x)(x)/(0.1-x)
Solve for x = (H^+), then convert to pH.
    
Step 2. Complete the ICE chart (initial, change. equilibrium).
Step 3. Write the Ka expression.
Step 4. Substitute the E line of the ICE chart into Ka expression and solve for the unknown.
.........HA ==> H^+ + A^-
I........0.1....0......0
C........-x.....x......x
E......0.1-x....x......x
Ka = (H^+)(A^-)/(HA)
4.5E-6 = (x)(x)/(0.1-x)
Solve for x = (H^+), then convert to pH.
                    Answered by
            Devin
            
    ph=10.3
    
                    Answered by
            Molly B
            
    The pH is not 10.3
    
                    Answered by
            Molly B
            
    I got that the pH equals 2.67 is this number correct?
    
                    Answered by
            DrBob222
            
    I don't get 2.67. If you will show your work I will find the error. I agree the answer isn't 10.3.
    
                    Answered by
            Cat
            
    The correct pH is 3.17
    
                    Answered by
            DrBob222
            
    3.17 is correct.
    
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