chemistry questions?

3.
Determine the pH and pOH of a solution which the [H⁺] = 0.00045 mol/L

pH = -log[H⁺] = -log(0.00045) = 3.3
pOH = pKw - pH = 14.0 - 3.3 = 10.7


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4.
What is the pH of a solution if the [OH⁻] = 2.2 × 10⁻⁶ mol/L ?

pOH = -log[OH⁻] = -log(2.2 × 10⁻⁶) = 5.7
pH = pKw - pOH = 14.0 - 5.7 = 8.3


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5.
Calculate the [H⁺] of a solution that has a pH of 2.8

[H⁺] = 10⁻²·⁸ M = 0.0016 M


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6.
What is the pH of a solution if the [OH⁻] = 3.5 × 10⁻³ mol/L

pOH = -log[OH⁻] = -log(3.5 × 10⁻³) = 2.5
pH = pKw - pOH = 14.0 - 2.5 = 11.5


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7.
Calculate the [H⁺] of a solution that has a pOH of 4.2

pH = pKw - pOH = 14.0 - 4.2 = 9.8
[H⁺] = 10⁻⁹·⁸ M = 1.6 × 10⁻¹⁰ M


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8.
Calculate the pOH of a solution if the [H⁺] = 5.2 × 10⁻³ mol/L

pH = -log[H⁺] = -log(5.2 × 10⁻³) = 2.3
pOH = pKw - pH = 14.0 - 2.3 = 11.7


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9.
Calculate the [OH⁻] of a solution that has a pH of 4.2

pOH = pKw - pH = 14.0 - 4.2 = 9.8
[OH⁻] = 10⁻⁹·⁸ M = 1.6 × 10⁻¹⁰ M


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10.
Calculate the [H⁺] and pH of a solution that has a [OH⁻] of 3.6 × 10⁻⁹ mol/L

[H⁺] = Kw / [H⁺] = (1.0 × 10⁻¹⁴) / (3.6 × 10⁻⁹) = 2.8 × 10⁻⁶ M
pH = -log[H⁺] = -log(2.8 × 10⁻⁶) = 5.6

All of these calculations can be done with 3 formulas:

pH = -log[H+]

pOH = -log[OH-] and,

pH + pOH = 14

If you just use the log (to the base 10) function on your calculator, these will be easy to solve.