Chemistry Help??? MULTIPLE CHOICE?

1.
Identify the conjugate base for HA in the following equation:
HA + H₂O ⇌ A⁻ + H₃O⁺

HA loses a proton (H⁺) to form A⁻ ion, while A⁻ ion gains a proton to form HA.
Hence, the conjugate base for HA is A⁻ ion.

The answer: d) A⁻


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2.
Consider the two concentration of H⁺ ions, 1 × 10⁻³ M and 3.2 × 10⁻³ M. Which will have the lower pH value?

The higher the concentration of H⁺ ions, the lower the pH is.
Since 3.2 × 10⁻³ M is a higher concentration, then it will have the lower pH value.

The answer: c) 3.2 × 10⁻³ M


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3.
If the concentration of OH⁻ ions is 2.7 × 10⁻⁹ M, what would the pOH be?

pOH = -log[OH⁻] = -log(2.7 × 10⁻⁹) = 8.57

The answer: 8.57


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4.
Phenolphthalein works in the range of pH 8 to 12.5 and turns pink in that range. What will occur if the indicator is placed in a 0.001 M KOH solution?

[OH⁻] = 0.001 M
pOH = -log(0.001) = 3
pH = pKw - pOH = 14 - 3 = 11
This falls into the range of pH 8 to 12.5, and thus the solution turns pink.

The answer: c) the solution will turn slightly pink.


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5. Distilled water has a pH of 7. Distilled water has:

pOH = pKw - pH = 14 - 7 = 7
Since, pH = pOH, then [H₃O⁺] = [OH⁻]

The answer: c) an equal number of H₃O⁺ and OH⁻ ions.

1. d)
2. c)
3. a)
4. c)
5. c)