IB Chemistry HL 3.1.9 Hl Poh Scale Questions

Use real HL exam questions to calculate pOH, interconvert pH and hydroxide concentration, and report strong-base pH at 298 K.

Exam points

Calculate pOH = −log₁₀[OH⁻] from a hydroxide ion concentration and report the logarithmic result with appropriate precision.
Convert between [H⁺], [OH⁻], pH and pOH using pH + pOH = 14 at 298 K when the stated water conditions allow it.
Apply hydroxide stoichiometry, dilution or excess-strong-base data before converting pOH to the final solution pH.

Learn this topic

Study 3.1.9 (HL)—pOH scale conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[Maximum number: 2]

Methanoic acid is a monoprotic weak acid.

The concentration of methanoic acid was found by titration with a $0.200 \mathrm{~mol} \mathrm{dm}^{-3}$ standard solution of sodium hydroxide, NaOH(aq), using an indicator to determine the end point.

Calculate the pH of the sodium hydroxide solution.

$[\mathrm{OH^-}]=0.200\ \mathrm{mol\ dm^{-3}}$

Alternative 1:
$\mathrm{pOH}=-\log(0.200)=0.699$ $\mathrm{pH}=14.000-0.699=13.301$

Alternative 2:
$[\mathrm{H^+}]=\frac{1.00\times10^{-14}}{0.200} =5.00\times10^{-14}\ \mathrm{mol\ dm^{-3}}$ $\mathrm{pH}=-\log(5.00\times10^{-14})=13.301$

All question bank results loaded

Learn this topic

IB Chemistry HL 3.1.9 Hl Poh Scale Questions question 1