Calculate the pH of a buffer from the pKa (or pKb) and the ratio of acid to conjugate base concentrations, work out the composition needed for a target pH, and explain why dilution does not change the pH of a buffer.
Tę umiejętność sprawdza 9 zadań wzorowanych na arkuszach IB z lat 2023–2026.
Some ionic compounds are the product of acid–base neutralization reactions. (i) State the names of the acid and the base that would produce sodium methanoate, HCOONa. (ii) Estimate the pH value of an aqueous solution of sodium methanoate. (iii) Ionic salts can…
A buffer solution can be prepared by mixing NH3(aq) with HCl(aq). (i) Describe how the two solutions should be combined so that the buffer obtained is as effective as possible. (ii) Write equations to show how this buffer solution responds to the…
A buffer solution contains propanoic acid at 0.300 mol dm−3 and sodium propanoate at 0.600 mol dm−3. What is its pH? pKa(propanoic acid) = 4.87 A. 4.57 B. 4.87 C. 5.17 D. 5.47
Methanoic acid, HCOOH, is a weak acid, and solutions of it are often used as acidic buffers. A chemist prepared a 0.500 mol dm−3 solution of methanoic acid, in which two conjugate acid–base pairs are present. (i) For each pair, state the…
(i) Describe how aqueous hexanoic acid and aqueous sodium hydroxide could be used to make a buffer solution. (ii) Predict the effect on the buffer's pH of adding a small amount of water.
A buffer solution of pH 5.35 contains ethanoic acid and its conjugate base, the ethanoate ion. The pKa of ethanoic acid is 4.76. The concentration of ethanoic acid in the buffer is 1.50 × 10−2 mol dm−3. Calculate…
Which combination would produce a buffer solution? A. 50 cm3 of 1.0 mol dm−3 NH3(aq) and 50 cm3 of 1.0 mol dm−3 HCl(aq) B. 25 cm3 of 1.0 mol dm−3…
A liquid medicine is buffered with carbonate ions and hydrogencarbonate ions. It contains 0.0120 mol dm−3 carbonate ions and 0.0300 mol dm−3 hydrogencarbonate ions. Ka (hydrogencarbonate ion) = 4.80 × 10−11.…
A neutralization curve for a weak acid, HA, titrated with a strong base is shown. (i) Estimate the pKa of HA. (ii) Explain, using an equation, why the pH changes very little when small volumes of strong base are added to the weak acid in the buffer…
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