Chemistry

Manual pH titration with Cobra4

Conductivity of various water samples

We examine our drinking water

Principle

This experiment shows how much the quality of drinking water of various locations in the same region can vary. The comparison of tap water with bottled mineral water and distilled water leads to surprising results.

Gas viscosity: estimation of molecular diameter

Principle

Expressed most simply, the viscosity of a fluid (liquid or gas) relates to its resistance to flow. The viscosity of a gas is determined in particular by the rate of transfer of the flow momentum from faster moving layers (laminas) to slower ones. The ...

Diffusion in gases: the diffusion coefficient of bromine in air

Principle

Diffusion arises from the flow of matter down a concentration gradient. In the evaporation method, a stationary concentration gradient is achieved in which the concentration decreases linearly with distance. Under these conditions the diffusion coeffi ...

Determination of the molecular mass of a liquid

Principle

The molar mass of a liquid is to be determined by evaporating a liquid at constant temperature and pressure, and measuring the volume of  vapour  formed using a calibrated gas syring.

Tasks

1. Determine the molar masses of diethy ...

Determining the molecular weight of a polymer from intrinsic viscosity measurements

Principle

The viscosity of a liquid is effectively determined by the strength of the intermolecular attractive forces. In the case of solutions, the viscosity of the solvent can alter significantly depending on the type and concentration of the solute. Due to their size, macr ...

Thermal conductivity of gases

Principle:

The thermal conductivity of different gases are measured with a gas-chromatographic thermal conductivity detector under stationary conditions. The electrical measurement parameter, which is obtained as a voltage signal in the experimental set-up, is proportional to ...

Gay-Lussac's law (with the Cobra3 Basic-Unit)

Principle

The state of a gas is determined by temperature, pressure and amount of substance. For the limiting case of ideal gases, these state variables are linked via the ideal gas law. For a change of state under isobaric conditions this equation converts Gay-Lussac's first ...

Charles's (Amontons') law (with the Cobra3 Basic-Unit)

Principle

The state of a gas is determined by temperature, pressure and amount of substance. For the limiting case of ideal gases, these state variables are linked via the ideal gas law. For a change of state under isochoric conditions this equation becomes Amontons' law.

Boyle-Mariotte law (with the Cobra3 Basic-Unit)

Principle

The state of a gas is determined by temperature, pressure and amount of substance. For the limiting case of ideal gases, these state variables are linked via the ideal gas law. In the case of isothermal process control this equation converts Boyle and Mariotte'slaw. ...

Determination of the adiabatic coefficient of gases

Principle

A mass oscillates on a volume of gas in a precision glass tube. The oscillationis maintained by leading escaping gas back into the system. The adiabatic coefficient of various gases is determined from the periodic time of the oscillation.

Heat capacity of gases

Priniciple

Heat is added to a gas in a glass vessel by an electric heater which is switched on briefly. The temperature increase results in a pressure increase, which is measured with a manometer. Under isobaric conditions, a temperature increase results in a v ...

Heat capacity of gases (with the Cobra3 Basic-Unit)

Priniciple:

Heat is added to a gas in a glass vessel by an electric heater which is switched on briefly. The temperature increase results in a pressure increase, which is measured with a manometer. Under isobaric conditions, a temperature increase results in a volume dilatatio ...

Determination of the enthalpy of vaporisation of liquids (with the Cobra3 Basic-Unit)

Principle

The vaporization of a liquid occurs with heat absorption. To determine the enthalpy of vaporization, a known mass of the liquid which is to be investigated is vaporized in a special vaporization vessel in a current of air. The quantity of heat absorbed, which corres ...