Which of the following is not a common use of sodium carbonate? (A) Sodium carbonate is the main ingredient in oven cleaners and drain-unclogging solutions. (B) Sodium carbonate is used to soften water by removing magnesium and calcium ions. (C) Sodium carbonate is added to silica and other compounds in the production of glass. (D) Plant material is boiled in sodium carbonate solution in the production of paper. Or (E) sodium carbonate is used for curing fibers as well as for dyeing and printing in the textile industry.
Every year, large quantities of sodium carbonate or Na2CO3 are produced. This is because it is easily dissolved in water and it produces a weakly basic solution that’s resistant to decomposition. Answer choice (A) involves sodium carbonate being used to clean ovens and unclog drains; however, these types of cleaners require a much more caustic chemical, like sodium hydroxide. And since we know that sodium carbonate is a weakly basic compound, we can say that answer choice (A) is not a common use of sodium carbonate.
Answer choice (B) states that sodium carbonate is used to soften water by removing magnesium and calcium ions. We know that sodium carbonate is highly water-soluble, but when it reacts with dissolved magnesium ions, magnesium carbonate precipitates out of solution, removing the magnesium from water. And when sodium carbonate reacts with calcium ions, a similar precipitation reaction occurs, removing the calcium ions from water. And because we know sodium carbonate removes magnesium and calcium ions from water, we know that answer choice (B) cannot be the correct answer.
Industrially, glass is made by mixing three main components together. Sand, which is mostly made up of silicon dioxide, is the main component. Because silicon dioxide has a very high melting point, sodium carbonate is also added to lower the melting point. And because sodium carbonate can change the chemistry of the glass, lime is added as a stabilizer. But since sodium carbonate is a major component added to silica to produce glass, we know that answer choice (C) cannot be the correct answer.
Paper is made in industry by separating out cellulose fibers from plant pulp. Because many of these plant materials are very tough, it requires boiling them in sodium carbonate solution. Sodium carbonate is used because it is water-soluble and it’s basic, which facilitates the breaking down of the plant pulp. And because of this, we can say that sodium carbonate is commonly used to produce paper. And so, we can eliminate answer choice (D).
Answer choice (E) states that sodium carbonate is used for curing fibers as well as for dyeing and printing in the textile industry. And again because of sodium carbonate’s water-soluble and basic properties, it can be used to promote the chemical reaction between fibers and dyes. And so, because sodium carbonate is used as a fixing agent to help cure fibers as well as dye them, we can eliminate answer choice (E) because it is a common use of sodium carbonate.
And so, because answer choices (B) through (E) are all common uses of sodium carbonate, we can correctly choose answer choice (A). Sodium carbonate is the main ingredient in oven cleaners and drain-unclogging solutions.