13. Read the text using the terminology from exercise 12 and describe the main principles of conductometry in the English language

Electrolytes are substances that produce free ions when they are placed into a solvent such as water. Their molecules split up into individual atomic components, which form ions, in a process called dissociation. Positively charged ions are cations, and those with a negative charge are anions. Due to the presence of free ions, electrolyte solutions behave as an electrically conductive medium.

Common electrolytes consist of salts, acids or bases. Electric properties of the conductor are described by Ohm's law I = U/R where I corresponds to a current, U is a voltage and R describes electric resistance. This resistance depends on the intrinsic properties of a conductor and on its shape as R = ρl/S where l is a conductor's length and S is a cross-sectional area. Every material is characterized by a specific resistance, ρ, that is given in units of Ω⋅m (Ω - ohm, a unit of electric resistance).

Electrical properties can be expressed also through the quantity, inverse to the resistance, conductivity. Its unit is S (Siemens), where 1S=1/Ω. Specific conductivity is inversely proportional to the specific resistance. It is expressed in units of S/m.

Conductometry means measuring the conductivity. A conductometer measures the electrical conductivity of ionic solutions. This is done by applying an electric field between two electrodes. The ions wander in this field. The anions migrate to the anode and the cations to the cathode.

The measuring unit used in conductivity measurements is the electrical resistance of the solution. This means that the conductivity is a sum parameter which includes all dissolved ions. Conductivity cannot be used for the determination of a single type of ion, unless the sample is a solution of a single salt or the concentrations of the other ions are known.

http://www.rjpbcs.com/pdf/2014_5(4)/[123].pdf

14. Watch the video using the link: http://www.youtube.com/watch?v=H3gLnwbn1bg and discuss the questions:

1. Briefly describe the experimental process.

2. Describe the main parts of the conductometer.

3. What are the modes of the conductometer?

4. Explain what property the engineer measured.

5. What solution did he use?

6. Explain how the engineer analyzed the obtained results.

7. Describe the linear function in the graph.

8. What is the practical application of the presented instrument?

9. Explain what you learnt from the experiment.

15. Translate the following sentences into the English language

1. Кондуктометрия – это метод для измерения электропроводности ионных растворов.

2. Электролит – это вещество, которое проводит электрический ток.

3. Примерами электролитов могут служить водные растворы кислот, солей и оснований.

4. Удельная электропроводность – это величина обратная удельному сопротивлению раствора.

5. Электрические свойства проводника описываются законом Ома.

6. Единицей измерения удельной проводимости является См/м.

7. Соль помещают в дистиллированную воду и перемешивают.

8. Для проведения эксперимента используется кондуктометрический датчик.

9. На графике показана линейная зависимость электросопротивления вещества от времени.

10. Кондуктометрия нашла широкое применение для исследования растворов твердых и жидких веществ в аналитической химии и на производстве.