Chemistry Help Please?

Determine the hydronium and hydroxide ion concentrations in a solution that is 2.0 × 10⁻² M NaOH.

NaOH is a strong alkali. 1 mole of NaOH completely dissociates in aqueous solution to give 1 mole of OH⁻ ions.
[OH⁻] = [NaOH]ₒ = 2.0 × 10⁻² M
[H₃O⁺] = Kw / [OH⁻] = (1.0 × 10⁻¹⁴) / (2.0 × 10⁻²) M = 5.0 × 10⁻¹³ M


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Determine the pH of a solution that is 5.0 × 10⁻⁴ M HNO₃.

HNO₃ is a strong acid. 1 mole of HNO₃ completely dissociates in aqueous solution to give 1 mole of H₃O⁺ ions.
[H₃O⁺] = [HNO₃]ₒ = 5.0 × 10⁻⁴ M
pH = -log[H₃O⁺] = -log(5.0 × 10⁻⁴) = 3.3


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Determine the pH of a 3.45 × 10⁻² M Sr(OH)₂ solution.

Sr(OH)₂ is a strong alkali. 1 mole of Sr(OH)₂ completely dissociates in aqueous solution to give 2 moles of OH⁻ ions.
[OH⁻] = 2 [Sr(OH)₂]ₒ = 2 × (3.45 × 10⁻² M) = 6.90 × 10⁻² M
pOH = -log[OH⁻] = -log(6.90 × 10⁻²) = 1.2
pH = pKw - pOH = 14.0 - 1.2 = 12.8

OR:
[H₃O⁺] = Kw/[OH⁻] = (1.00 × 10⁻¹⁴) / (6.90 × 10⁻²) M = 1.45 × 10⁻¹³ M
pH = -log[H₃O⁺] = -log(1.45 × 10⁻¹³) = 12.8


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The pH of a solution is determined to be 7.0. What is the hydronium ion concentration of this solution?

[H₃O⁺] = 10^(-pH) M = 10^(-7.0) M = 1.0 × 10⁻⁷ M


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The pH of an aqueous solution is measured as 5.00. Calculate the [H₃O⁺] and the [OH⁻]

[H₃O⁺] = 10^(-pH) M = 10^(5.00) M = 1.00 × 10⁻⁵ M
[OH⁻] = Kw / [H₃O⁺] = (1.00 × 10⁻¹⁴) / (1.00 × 10⁻⁵) M = 1.00 × 10⁻⁹ M