Rocks & minerals, separation techniques: distillation, crystallization, filtration：練習問題

A student performs a simple distillation to obtain pure water from a sample of sea water. Which of the following statements concerning the laboratory procedure are correct?

(1) Anti-bumping granules are added to the distillation flask to ensure smooth boiling.
(2) The cooling water should enter the condenser from the lower opening and leave from the upper opening.
(3) The thermometer bulb should be immersed in the sea water to accurately monitor the boiling point of the distillate being collected.

A chemist is tasked with separating a complex mixture containing three solid components: insoluble fine sand ( \(\text{SiO}_2\) ), sodium chloride ( \(\text{NaCl}\) ), and copper(II) sulfate ( \(\text{CuSO}_4\) ). The solubilities in \(100 \text{g}\) of water are: \(\text{NaCl}\) , \(\sim 36 \text{g}\) at \(0^{\circ}\text{C}\) and \(\sim 40 \text{g}\) at \(100^{\circ}\text{C}\) ; \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\) , \(\sim 32 \text{g}\) at \(0^{\circ}\text{C}\) and \(\sim 200 \text{g}\) at \(100^{\circ}\text{C}\) . The goal is to obtain pure, hydrated copper(II) sulfate crystals ( \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\) ) using the following proposed steps:

I. Dissolve the mixture in a moderate amount of hot distilled water.
II. Filter the resulting mixture to remove the sand.
III. Evaporate the filtrate to reduce the volume significantly, and then cool the concentrated solution slowly to obtain solid residue X.
IV. Recrystallize solid residue X to purify it.

Which modification to Step III would make the overall separation procedure most efficient for obtaining pure \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\) crystals, minimizing the contamination in residue X?

A solid mixture contains ammonium chloride, iron filings, and copper(II) sulfate. Which of the following sequences of operations is most appropriate to separate these components into their pure forms?

A student is provided with a powdered rock sample which is a mixture of silver oxide, silicon dioxide (sand), and sodium carbonate. The following experimental procedures are carried out in a school laboratory:

Step 1: Add excess distilled water to the sample, stir well, and filter to obtain a residue and a filtrate.
Step 2: Heat the residue strongly in a test tube and test any gas produced with a glowing splint.
Step 3: Add dilute hydrochloric acid to the filtrate and pass any gas produced into limewater (calcium hydroxide solution).

Which of the following statements concerning the experiments are correct?
(1) The gas produced in Step 2 can relight a glowing splint.
(2) The gas produced in Step 3 turns limewater milky.
(3) The solid remaining in the test tube after Step 2 is a pure element.

A student is provided with a crushed rock sample containing limestone, silver oxide, and a small amount of common salt. The student carries out the following procedure:

Step I: Add excess distilled water to the sample, stir well, and filter.
Step II: Heat the residue from Step I strongly in a crucible for several minutes.
Step III: Heat the filtrate from Step I until it is saturated, then allow it to cool slowly to form crystals.

Which of the following statements concerning the above procedure are correct?
(1) The solid remaining in the crucible after Step II is a mixture of a metal and a metal oxide.
(2) Step III is more appropriate than evaporating the filtrate to dryness for obtaining the salt in a pure state.
(3) A gas that turns limewater milky is evolved during Step II.

A solid mixture contains silver oxide and calcium carbonate. Explain how heating the mixture strongly followed by the addition of excess dilute hydrochloric acid and filtration can be used to obtain silver metal, including the word equation for the decomposition of the carbonate component.