More About Acids (DP IB Chemistry: SL)

The equilibrium constant for the first dissociation of formic acid is 1.8 x 10^-4 mol dm^-3.

State, with a reason, the strength of formic acid.

Outline one laboratory method used to distinguish between equimolar solutions of formic acid and hydrochloric acid, giving the expected observations.

Formic acid has the chemical formula HCOOH. Identify the conjugate base of formic acid and state whether it is a weak or strong conjugate base.

Draw the structure of formic acid and give its systematic IUPAC name.

The pH of an aqueous solution of salicylic acid at 298 K is 3.85. Determine the concentration of hydroxide ions in the solution, using Section 2 of the Data booklet.

A and B are two solutions of the same concentrations that have pH values of 3 and 6 respectively. 

The variation of conductivity and concentration of a strong and weak monoprotic acid are shown in Figure 1.

Identify the strong and weak acid from the information given and justify your choices.

For acid 1 and acid 2 in part (c) compare the volume of 0.2 mol dm^-3 NaOH required to neutralise 20 cm³ of 0.1 mol dm^-3 solutions of the acids.

The concentrations of solutions of weak acids can be determined by titration against standard solutions of alkalis, such as sodium hydroxide.

A solution of 25.0 cm³ ethanoic acid was titrated against 0.150 mol dm^-3 NaOH (aq) and it was found that 22.35 cm³ of the NaOH was needed for complete neutralisation.

Write an equation for the reaction and determine the concentration of the ethanoic acid.

A solution of 0.1 mol dm^-3 ammonia has a pH of approximately 11. Predict how the pH value of 0.1 mol dm^-3 sodium hydroxide solution would compare and calculate its value.

Write an equation for the reaction between ammonia and water and use it to classify each product as a Brønsted–Lowry acid or base.

Glycolic acid, C₂H₄O₃, is an organic acid sometimes used to remove limescale, CaCO₃, from electric kettles and coffee machines.

Predict, with a reason, a difference in the reaction between the same concentration of sulfuric acid and glycolic acid with samples of calcium carbonate.

Another acid that is sometimes used to descale kettles is sulfamic acid, NH₂SO₃H. Sulfamic is classed as a strong monoprotic acid.

A solution of hydrochloric acid has a pH of 1 and a solution of carbonic acid has a pH of 5. Determine the ratio of hydrogen ion concentrations of hydrochloric acid to carbonic acid.

Outline two ways, apart from using pH, which could allow you to distinguish between two solutions of carbonic acid and hydrochloric acid that have the same concentration.

Four solutions of acids with identical concentrations are prepared. The equilibrium constants of these acids are given in Table 1.

Table 1

Write down the acid dissociation equation for HCN.

Use the information in part (a) to complete this question.

State the name and formula of all the chemical species present in the solution of CH₃COOH.

Write the name and formula of the conjugate base of HF.

A solution of hydrochloric acid of concentration 0.001 mol dm^-3 has a pH value of 3. Suggest, giving a reason, the pH of the following solutions of acids:

A solution of 0.01 mol dm^-3 ethanoic acid has a concentration of hydrogen ion of 1 x 10^-4 mol dm^-3.  Determine the percentage of ethanoic acid molecules that have dissociated.

Two separate titrations are carried out using 25.00 cm³ of 0.01 mol dm^-3 solutions of hydrochloric acid followed by ethanoic acid, against 0.01 mol dm^-3 sodium hydroxide. 

State what difference(s) would be observed in the two titrations.  

Suggest a suitable indicator for the titration of hydrochloric acid and sodium hydroxide in part c), and state the colour changes observed.

Show how the ionic product for water is derived from the dissociation of water and give it units.

Determine the pH of 0.001 mol dm^-3 sodium hydroxide.

Suggest, with a reason, how the magnitude of K_w changes with increasing temperature.

Malonic acid is a weak dibasic carboxylic acid with the formula C₃H₄O₄. Draw the displayed structure of malonic acid.

Suggest, with a reason, which of the two acids, ethanoic or malonic, has a higher pH?

Apart from testing the pH, suggest how equimolar solutions of malonic acid and ethanoic acid may be distinguished.

Write the formulas of two conjugate bases that can be formed from malonic acid.

Marble chips are added separately to solutions of the same concentration of ethanoic acid and hydrochloric acid. State one similarity and one difference you would expect to observe in the reactions.

Write an equation for the reaction between marble chips and ethanoic acid.

Determine the volume, in cm³, of 2.25 mol dm^-3 ethanoic acid needed to completely react with 1.50 g of marble chips. 

Determine the volume of CO₂, in cm³, produced at 273 K and 101 kPa in part c).