Topic 14: Acid-base Equilibria

Understand that a Brønsted–Lowry acid is a proton donor and a Brønsted–Lowry base is a proton acceptor and that acid-base reactions involve proton transfer.

Use —a brønsted–lowry acid is a proton donor and a brønsted–lowry base is a proton acceptor and that acid-base reactions involve to connect the rule to the data and decision in the question.

This matters because —a brønsted–lowry acid is a proton donor and a brønsted–lowry base is a proton acceptor and that acid-base reactions involve determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —a brønsted–lowry acid is a proton donor and a brønsted–lowry base is a proton acceptor and that acid-base reactions involve to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —A Brønsted–Lowry acid is a proton donor and a Brønsted–Lowry base is a proton acceptor and that acid-base reactions involve is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to identify Brønsted–Lowry conjugate acid-base pairs.

Use —identify brønsted–lowry conjugate acid-base pairs to connect the rule to the data and decision in the question.

This matters because —identify brønsted–lowry conjugate acid-base pairs determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —identify brønsted–lowry conjugate acid-base pairs to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Identify Brønsted–Lowry conjugate acid-base pairs is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to define the term ‘pH’.

Use —define the term ‘ph’ to connect the rule to the data and decision in the question.

This matters because —define the term ‘ph’ determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —define the term ‘ph’ to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Define the term ‘pH’ is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate pH from hydrogen ion concentration.

Use —ph from hydrogen ion concentration to connect the rule to the data and decision in the question.

This matters because —ph from hydrogen ion concentration determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —ph from hydrogen ion concentration to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —PH from hydrogen ion concentration is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Calculate hydrogen-ion concentration in mol dm−3 from pH using [H+] = 10^(−pH).

Use —hydrogen-ion concentration in mol dm−3 from ph using [h+] = 10^(−ph) to connect the rule to the data and decision in the question.

This matters because —hydrogen-ion concentration in mol dm−3 from ph using [h+] = 10^(−ph) determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —hydrogen-ion concentration in mol dm−3 from ph using [h+] = 10^(−ph) to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Hydrogen-ion concentration in mol dm−3 from pH using [H+] = 10^(−pH) is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand the difference between a strong acid and a weak acid in terms of the degree of dissociation.

Use —the difference between a strong acid and a weak acid in terms of the degree of dissociation to connect the rule to the data and decision in the question.

This matters because —the difference between a strong acid and a weak acid in terms of the degree of dissociation determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the difference between a strong acid and a weak acid in terms of the degree of dissociation to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The difference between a strong acid and a weak acid in terms of the degree of dissociation is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate the pH of a strong acid.

Use —the ph of a strong acid to connect the rule to the data and decision in the question.

This matters because —the ph of a strong acid determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the ph of a strong acid to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The pH of a strong acid is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to deduce the expression for the acid dissociation constant, Ka, for a weak acid.

Use —deduce the expression for the acid dissociation constant, ka, for a weak acid to connect the rule to the data and decision in the question.

This matters because —deduce the expression for the acid dissociation constant, ka, for a weak acid determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —deduce the expression for the acid dissociation constant, ka, for a weak acid to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Deduce the expression for the acid dissociation constant, Ka, for a weak acid is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate the pH of a weak acid from Ka or pKa values, making relevant assumptions Students will not be expected to solve quadratic equations.

Use —the ph of a weak acid from ka or pka values, making relevant assumptions students will not be expected to solve quadratic to connect the rule to the data and decision in the question.

This matters because —the ph of a weak acid from ka or pka values, making relevant assumptions students will not be expected to solve quadratic determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the ph of a weak acid from ka or pka values, making relevant assumptions students will not be expected to solve quadratic to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The pH of a weak acid from Ka or pKa values, making relevant assumptions Students will not be expected to solve quadratic is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to define the ionic product of water, Kw.

Use —define the ionic product of water, kw to connect the rule to the data and decision in the question.

This matters because —define the ionic product of water, kw determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —define the ionic product of water, kw to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Define the ionic product of water, Kw is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate the pH of a strong base from its concentration, using Kw or pKw.

Use —the ph of a strong base from its concentration to connect the rule to the data and decision in the question.

This matters because —the ph of a strong base from its concentration determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the ph of a strong base from its concentration to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The pH of a strong base from its concentration is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to define the terms ‘pKa’ and ‘pKw’.

Use —define the terms ‘pka’ and ‘pkw’ to connect the rule to the data and decision in the question.

This matters because —define the terms ‘pka’ and ‘pkw’ determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —define the terms ‘pka’ and ‘pkw’ to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Define the terms ‘pKa’ and ‘pKw’ is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to analyse data from the following experiments: i measuring the pH of a variety of substances, including equimolar solutions of strong and weak acids, strong and weak bases, and salts ii comparing the pH of a strong and weak acid after dilution 10, 100 and 1000 times.

Use —analyse data from the following experiments: i measuring the ph of a variety of substances to connect the rule to the data and decision in the question.

This matters because —analyse data from the following experiments: i measuring the ph of a variety of substances determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —analyse data from the following experiments: i measuring the ph of a variety of substances to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Analyse data from the following experiments: i measuring the pH of a variety of substances is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate Ka for a weak acid from experimental data given the pH of a solution containing a known mass of acid.

Use —ka for a weak acid from experimental data given the ph of a solution containing a known mass of acid to connect the rule to the data and decision in the question.

This matters because —ka for a weak acid from experimental data given the ph of a solution containing a known mass of acid determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —ka for a weak acid from experimental data given the ph of a solution containing a known mass of acid to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Ka for a weak acid from experimental data given the pH of a solution containing a known mass of acid is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to draw and interpret titration curves, using all combinations of strong and weak monoprotic and diprotic acids with bases, and apply these principles to diprotic acids and bases.

Use —draw and interpret titration curves to connect the rule to the data and decision in the question.

This matters because —draw and interpret titration curves determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —draw and interpret titration curves to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Draw and interpret titration curves is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to select a suitable indicator for a titration, using a titration curve and appropriate data.

Use —select a suitable indicator for a titration to connect the rule to the data and decision in the question.

This matters because —select a suitable indicator for a titration determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —select a suitable indicator for a titration to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Select a suitable indicator for a titration is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Know what is meant by the term ‘buffer solution’.

Use —what is meant by the term ‘buffer solution’ to connect the rule to the data and decision in the question.

This matters because —what is meant by the term ‘buffer solution’ determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —what is meant by the term ‘buffer solution’ to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —What is meant by the term ‘buffer solution’ is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand the action of a buffer solution.

Use —the action of a buffer solution to connect the rule to the data and decision in the question.

This matters because —the action of a buffer solution determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the action of a buffer solution to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The action of a buffer solution is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate the pH of a buffer solution given appropriate data.

Use —the ph of a buffer solution given appropriate data to connect the rule to the data and decision in the question.

This matters because —the ph of a buffer solution given appropriate data determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the ph of a buffer solution given appropriate data to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The pH of a buffer solution given appropriate data is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Be able to calculate the concentrations of solutions required to prepare a buffer solution of a given pH.

Use —the concentrations of solutions required to prepare a buffer solution of a given ph to connect the rule to the data and decision in the question.

This matters because —the concentrations of solutions required to prepare a buffer solution of a given ph determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the concentrations of solutions required to prepare a buffer solution of a given ph to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The concentrations of solutions required to prepare a buffer solution of a given pH is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand how to use a weak acid-strong base or strong acid-weak base titration curve to: i demonstrate buffer action ii determine Ka from the pH at the point where half the acid is neutralised/ equivalence point.

Use —how to use a weak acid-strong base or strong acid-weak base titration curve to: i demonstrate buffer action ii determine ka to connect the rule to the data and decision in the question.

This matters because —how to use a weak acid-strong base or strong acid-weak base titration curve to: i demonstrate buffer action ii determine ka determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —how to use a weak acid-strong base or strong acid-weak base titration curve to: i demonstrate buffer action ii determine ka to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —How to use a weak acid-strong base or strong acid-weak base titration curve to: i demonstrate buffer action ii determine Ka is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

Understand the importance of buffer solutions in biological environments: i buffers in cells and in blood (H2CO3/HCO-3) ii in foods to prevent deterioration due to pH change (caused by bacterial or fungal activity).

Use —the importance of buffer solutions in biological environments: i buffers in cells and in blood (h2co3/hco-3) ii in foods to connect the rule to the data and decision in the question.

This matters because —the importance of buffer solutions in biological environments: i buffers in cells and in blood (h2co3/hco-3) ii in foods determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —the importance of buffer solutions in biological environments: i buffers in cells and in blood (h2co3/hco-3) ii in foods to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —The importance of buffer solutions in biological environments: i buffers in cells and in blood (H2CO3/HCO-3) ii in foods is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.

CORE PRACTICAL 11 Finding the Ka value for a weak acid.

Use —core practical 11 finding the ka value for a weak acid to connect the rule to the data and decision in the question.

This matters because —core practical 11 finding the ka value for a weak acid determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —core practical 11 finding the ka value for a weak acid to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —CORE PRACTICAL 11 Finding the Ka value for a weak acid is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.