Acids, bases and salts：練習題

A student tests a solution with litmus and methyl orange indicators. The litmus turns red and the methyl orange turns red.

What can be concluded about the solution?

Which of the following describes a basic oxide?

Elements X and Y belong to the same period of the Periodic Table. The oxide of X is found to be basic, while the oxide of Y is found to be acidic.

Which statement correctly compares elements X and Y?

Which statement correctly describes a base according to the IGCSE syllabus?

A student needs to prepare a sample of an insoluble salt. Which experimental technique should they use?

Describe the effect of an alkali on the colour of litmus indicator.

A chemist wants to prepare a sample of magnesium sulfate by reacting excess magnesium ribbon with dilute sulfuric acid. Explain why using an excess of the metal is necessary in this preparation.

Define the term alkali in relation to bases.

The preparation of a pure, dry sample of a soluble salt can be achieved through different experimental routes depending on the solubility of the reactants.

(a) Magnesium sulfate is a soluble salt. Suggest the names of an acid and an insoluble base that could be reacted together to produce magnesium sulfate.
(b) In the preparation of magnesium sulfate using the reactants from part (a), why is the insoluble base added in excess?
(c) Describe how the excess insoluble base is removed from the reaction mixture before the salt is crystallized.
(d) Outline the steps needed to obtain large, dry crystals of magnesium sulfate from the resulting solution.

A chemist needs to prepare a pure, dry sample of the soluble salt zinc sulfate.

(a) Suggest the names of two reactants that could be reacted together to form zinc sulfate and water only.
(b) Describe the experimental steps required to obtain a pure, dry sample of zinc sulfate crystals, starting from the reactants named in part (a).
(c) Describe how the presence of sulfate ions in the resulting solution could be confirmed using aqueous barium nitrate and dilute nitric acid. State the expected observation.