QuestionBEST Completer the statement or anwers the quetion.
following reaction will ?
B)
C)
D)
E)
7. Express the equilibrium constant for the following reaction.
A)
B)
C)
D)
E)
8. A solution is prepared by dissolving 0.23 mol of benzoic acid and 0.27 mol of potassium benzoate in sufficient water to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer soltation causes the pH to decrease only slighly. The pH does not decrease drastically because the HCl reacts with the present in the buffer solution.
A)
B)
O) porassium ion
D) benzoic acíd
E) benzoate ion
9. A 50.0 mL sample of an aqueous solution is titrated with a 0.375 M NaOH solution. The equivalence point is reached upon addition of 125.1 mL of the base. The concentration of is .
A) 0.234
B) 0.469
C) 0.150
D) 0.300
E) 0.938
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Studdy Solution
STEP 1
What is this asking?
We need to find which reaction has , write the equilibrium constant for a reaction involving a solid, figure out why adding HCl to a buffer doesn't change the pH much, and calculate the concentration of sulfuric acid given titration data.
Watch out!
Remember solids don't appear in equilibrium expressions, and strong acids react completely with conjugate bases in buffer solutions.
Don't forget the stoichiometry when dealing with acids and bases!
STEP 2
1. Find the reaction where
2. Write the equilibrium constant expression
3. Explain the buffer behavior
4. Calculate the sulfuric acid concentration
STEP 3
Remember, the relationship between and is given by , where is the change in the number of moles of gas.
STEP 4
We're looking for a reaction where .
This happens when .
Let's check each reaction:
* B) = 4 - 2 = 2.
Nope!
* C) = 2 - 2 = 0.
Bingo! This is it!
* D) = 1 - 3 = -2.
Nope!
* E) = 1 - 3 = -2.
Nope!
STEP 5
So, the answer is C, where , making .
STEP 6
Remember, solids and pure liquids don't show up in equilibrium constant expressions!
STEP 7
For the reaction , since is a solid, it won't be included in our expression.
So, .
STEP 8
This matches answer D, if we rewrite our expression as .
STEP 9
Buffers resist pH changes because they contain a weak acid and its conjugate base (or a weak base and its conjugate acid).
STEP 10
When we add HCl, a strong acid, it reacts completely with the **benzoate ion**, the conjugate base.
This reaction consumes the added ions, preventing a drastic pH change.
STEP 11
The answer is **E**, benzoate ion.
STEP 12
The balanced reaction is: .
STEP 13
We have of NaOH, so the number of moles of NaOH is .
STEP 14
From the balanced equation, moles of NaOH react with mole of .
So, the moles of are .
STEP 15
The concentration of is .
STEP 16
The answer is **B**, 0.469 M.
STEP 17
The answers are: C, D, E, and B.
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