Question Video: Recalling the Solution Used to Test the Gas Given Off by a Carbonate Anion Reacting with an Acid | Nagwa Question Video: Recalling the Solution Used to Test the Gas Given Off by a Carbonate Anion Reacting with an Acid | Nagwa

Question Video: Recalling the Solution Used to Test the Gas Given Off by a Carbonate Anion Reacting with an Acid Chemistry • Third Year of Secondary School

When testing for the carbonate anion using dilute hydrochloric acid, through which of the following solutions is the gas produced commonly passed? [A] Acidified potassium permanganate [B] Acidified potassium dichromate [C] Limewater [D] Barium chloride [E] Silver nitrate

03:33

Video Transcript

When testing for the carbonate anion using dilute hydrochloric acid, through which of the following solutions is the gas produced commonly passed? (A) Acidified potassium permanganate, (B) acidified potassium dichromate, (C) limewater, (D) barium chloride, (E) silver nitrate.

The carbonate anion is a negatively charged ion and it has the formula CO32−. If we were to put a sample of a carbonate-containing rock, like limestone, into hydrochloric acid, we’d see signs of a chemical reaction starting immediately. Bubbles of gas or effervescence will be observed. This is a sure sign that carbon dioxide gas is being produced in this reaction. The carbonate ions in the rock reacts with hydrogen ions from the acid to produce carbon dioxide gas and water. So in the test for carbonate anions, a sample is introduced into a test tube containing some hydrochloric acid. Effervescence would immediately be observed, but this doesn’t prove that the gas is carbon dioxide.

To confirm the presence of carbonate ions in the sample, what we need is a simple test to prove that the gas bubbles are indeed carbon dioxide gas. The simplest way to test for carbon dioxide is to bubble it through a solution of limewater. Limewater is a saturated solution of calcium hydroxide. Most importantly in the test, calcium hydroxide reacts with carbon dioxide and it turns cloudy or milky looking. The cloudiness or milkiness that is observed in this test is due to the formation of a white precipitate of calcium carbonate. So the solution that the gas should be passed through in this chemical test for carbonate ions is limewater.

Solutions of acidified potassium permanganate and acidified potassium dichromate are both powerful oxidizing agents. As oxidizing agents, they can be used to test for reducing agents, such as sulfur dioxide gas, for example. These oxidizing agents are not the correct answer here.

A solution of barium chloride will contain aqueous barium ions. Barium chloride solution can be used to test for sulfate anions. In this test, a dense white precipitate of barium sulfate is produced. Barium chloride is not used to test for carbon dioxide gas. It’s not the correct answer. Silver nitrate is very soluble in water and solutions of silver nitrate contain silver ions. Silver nitrate solution is frequently used as part of a test for halide ions, such as chloride, bromide, and iodide. It’s not used as a test for carbon dioxide gas and it’s not the correct answer.

When testing for the carbonate anion using dilute hydrochloric acid, through which of the following solutions is the gas produced commonly passed? We must choose answer choice (C). The correct answer is limewater.

Join Nagwa Classes

Attend live sessions on Nagwa Classes to boost your learning with guidance and advice from an expert teacher!

  • Interactive Sessions
  • Chat & Messaging
  • Realistic Exam Questions

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy