生成这个题目的讲解---Here is the extracted content from the image: **Problem 4:** **Question Stem:** A school's extracurricular activity group designed the experiment shown in the figure to investigate if the gas produced by the reaction of copper with dilute nitric acid is NO. During the experiment, nitrogen oxides produced were simultaneously absorbed by limewater to obtain the widely used Ca(NO₂)₂. The experimental setup is shown in the figure. (Known: NO + NO₂ + 2OH⁻ = 2NO₂⁻ + H₂O, 2NO₂ + 2OH⁻ = NO₃⁻ + NO₂⁻ + H₂O) **Chart/Diagram Description:** * **Type:** Chemical experimental setup diagram. * **Overall Layout:** The diagram shows a series of four interconnected chemical apparatuses (labeled A, B, C, D) arranged horizontally from left to right, with gas flowing sequentially through them. * **Main Elements:** * **Gas Inlet (Left):** An arrow indicates "N₂" (nitrogen gas) entering, controlled by a stopcock labeled "K". * **Apparatus A (Test Tube):** Contains "稀硝酸" (dilute nitric acid) and a "铜丝" (copper wire) partially submerged in the acid. It has a gas outlet tube connected to Apparatus B. Labeled "A". * **Apparatus B (Round-Bottom Flask):** Connected to the outlet of Apparatus A. It has an internal tube extending downwards, labeled "E". A side arm branches off, connected to a syringe or gas inlet labeled "空气" (air) and an additional label "F" (likely indicating the syringe connection point). An outlet tube connects to Apparatus C. Labeled "B". * **Apparatus C (Test Tube):** Contains "澄清石灰水" (clear limewater). It has a gas inlet tube connected from Apparatus B and an outlet tube connected to Apparatus D. Labeled "C". * **Apparatus D (Beaker with Inverted Funnel):** A beaker containing "NaOH溶液" (NaOH solution). An inverted funnel, connected to the outlet of Apparatus C, is submerged in the NaOH solution. Labeled "D". **Sub-questions:** **(1)** 实验之前通入 N₂ 的目的是 (Purpose of introducing N₂ before the experiment is to) **(2)** 在(1)操作后将装置 A 中铜丝插入稀硝酸, 溶液显蓝色, 有无色气体生成, 该反应中表现氧化性的硝酸与参与反应的硝酸物质的量之比为 ____。 (After operation (1), insert the copper wire in apparatus A into the dilute nitric acid. The solution turns blue, and a colorless gas is produced. In this reaction, the ratio of the amount of nitric acid acting as an oxidizing agent to the total amount of nitric acid participating in the reaction is ____.) **(3)** 装置 B 中用注射器压入空气之后现象是 ____。 (The phenomenon after air is injected into apparatus B with a syringe is ____.) **(4)** D 装置的作用是 ____。 (The function of apparatus D is to ____.) **Additional Text:** 提醒:完成作业 8 (Hint: Complete Homework 8)