酸、鹼與鹽：练习题

Which of the following substances has a pH value less than 7?

Consider two monoprotic acids, Acid X and Acid Y. At 298 K, a 0.1 mol dm\(^{-3}\) solution of Acid X has a pH of 1.0, while a 0.1 mol dm\(^{-3}\) solution of Acid Y has a pH of 2.8. Which of the following conclusions is correct?

A 0.010 mol dm\(^{-3}\) solution of a weak acid \( HA \) is 2.0% ionized. What is the acid dissociation constant \( K_{a} \) for this acid?

A solution of a strong acid with concentration \( 0.01 \text{ mol dm}^{-3} \) is diluted by a factor of 100. What is the pH of the resulting solution at \( 25^\circ\text{C} \)?

Calculate the volume of \( 0.050 \text{ mol dm}^{-3} \) sulfuric acid, \( \text{H}_2\text{SO}_4 \), required to completely neutralize \( 20.0 \text{ cm}^3 \) of \( 0.150 \text{ mol dm}^{-3} \) potassium hydroxide, \( \text{KOH} \).

Predict whether a solution of ammonium chloride, \(\text{NH}_4\text{Cl}\), will be acidic, basic, or neutral. Provide the ionic equation for the hydrolysis reaction that occurs between the ammonium ion and water to support your answer.

Calculate the \(\text{pH}\) of a solution formed by mixing \(50.0\text{ cm}^3\) of \(0.20\text{ mol dm}^{-3}\) \(\text{HCl}\) with \(50.0\text{ cm}^3\) of \(0.10\text{ mol dm}^{-3}\) \(\text{NaOH}\). Assume the volumes are additive and the temperature is \(25^{\circ}\text{C}\).

A student titrates \(25.0\text{ cm}^3\) of a dilute sulfuric acid solution with \(0.10\text{ mol dm}^{-3}\) sodium hydroxide. If \(20.0\text{ cm}^3\) of sodium hydroxide is required for neutralization, calculate the molarity of the sulfuric acid. Write the balanced chemical equation for this reaction.

A student is investigating the properties of a 0.1 M solution of ethanoic acid (\(CH_{3}COOH\)).
(a) Write a chemical equation to show the partial ionization of ethanoic acid in water and explain why it is classified as a weak acid.
(b) The student then adds a few drops of universal indicator to the solution. State the expected color of the indicator and estimate the pH value.
(c) If 10 \(cm^{3}\) of 0.1 M sodium hydroxide (\(NaOH\)) is added to 20 \(cm^{3}\) of 0.1 M ethanoic acid, will the resulting solution be acidic, basic, or neutral? Explain your reasoning.

An unknown solid X is suspected to be a carbonate salt. A student performs a series of tests to identify it.
(a) When dilute nitric acid is added to X, vigorous effervescence occurs and a colorless gas is evolved. Describe how you would test this gas and state the expected observation.
(b) The resulting solution from part (a) is colorless. When a small amount of dilute sodium hydroxide is added, a white precipitate forms which dissolves in excess sodium hydroxide to form a colorless solution. Identify the metal ion present in X.
(c) Based on your findings, provide the chemical formula for X and write the ionic equation for the reaction between X and nitric acid.