Question

Убираясь в лаборатории перед уроком, лаборант обнаружил, что от склянок с растворами солей отпали этикетки с надписями: Na2CO3; Al2(SO4)3; NaCl. Времени для приготовления новых растворов не было. Лаборант решил воспользоваться лакмусом и вернуть этикетки на склянки с растворами солей. Он взял три пробирки налил в них растворы солей из каждой колбы. Затем добавил к каждой пробирке 2-3 капли индикатора лакмуса. В первой пробирке раствор окрасился в голубой цвет, во второй пробирке остался без изменения, а в третьей пробирке стал красным. Надписи были восстановлены. А сможете ли вы сказать, в какой колбе находился раствор каждой соли? Чем руководствовался лаборант при использовании лакмуса? Каким еще способом можно было провести определение?

Answer 1

Na2CO3 синий (щелочная среда, сильное основание и слабая кислота) NaCl бесцветный (нейтральная среда, сильное основание и сильна бы кислота) Al2(SO4)3 красный (среда кислая, слабое основание и сильная кислота) Помимо лакмуса есть другие индикаторы: фенолфталеин, метил-оранж и т.д. Так же можно было провести качественные реакции на анионы.

Answer 2

Identifying the Solutions Using Litmus Paper

The lab assistant used litmus paper to identify the solutions in the flasks. Litmus paper is a type of indicator paper that changes color in the presence of an acid or a base. It can be used to determine the pH of a solution.

In this case, the lab assistant added a few drops of litmus indicator to each of the three test tubes containing the solutions. Based on the color changes observed, the lab assistant was able to identify the solutions.

- The solution in the first test tube turned blue. - The solution in the second test tube remained unchanged. - The solution in the third test tube turned red.

By comparing these color changes with the known color changes of litmus paper in the presence of acids and bases, the lab assistant was able to determine the identity of each solution.

Using Litmus Paper as an Indicator

Litmus paper is an indicator that changes color in the presence of an acid or a base. It contains a mixture of dyes that are sensitive to changes in pH. When the litmus paper is exposed to an acidic solution, it turns red. On the other hand, when it is exposed to a basic solution, it turns blue.

In this case, the lab assistant used litmus paper to determine the pH of the solutions in the test tubes. The color changes observed in the test tubes indicated the presence of acids or bases in the solutions.

Based on the color changes observed, the lab assistant made the following conclusions:

- The solution in the first test tube turned blue, indicating that it was a basic solution. - The solution in the second test tube remained unchanged, indicating that it was a neutral solution. - The solution in the third test tube turned red, indicating that it was an acidic solution.

By comparing these observations with the known properties of the salts, the lab assistant was able to identify the solutions.

Alternative Methods for Determining the Solutions

Apart from using litmus paper, there are other methods that can be used to determine the identity of the solutions. Some of these methods include:

1. Chemical Reactions: Each salt has its own unique chemical properties that can be used to identify it. By performing specific chemical reactions with the solutions, the lab assistant could have observed characteristic changes in color, precipitation, or gas formation that would have allowed them to identify the salts.

2. Spectroscopy: Spectroscopic techniques, such as infrared spectroscopy or atomic absorption spectroscopy, can be used to analyze the composition of a solution. By comparing the obtained spectra with reference spectra of known salts, the lab assistant could have identified the solutions.

3. Solubility Tests: Each salt has a specific solubility in water. By performing solubility tests, the lab assistant could have determined the solubility of each salt and used that information to identify the solutions.

These are just a few examples of alternative methods that could have been used to determine the identity of the solutions. The choice of method depends on the available equipment, time constraints, and the specific properties of the substances being tested.