Introduction:
The Hall effect is a phenomenon in which a voltage difference is developed across a conductor when it is subjected to a magnetic field perpendicular to the current flow. This effect can be utilized to measure various properties of a material. However, there are certain quantities that cannot be determined using the Hall effect.

Explanation:
The Hall effect can be used to measure several properties of a material, including mobility of charge carriers, carrier concentration, and type of semiconductor (p or n). However, it cannot be used to determine the diffusion constant.

Mobility of charge carriers:
The Hall effect provides a means to determine the mobility of charge carriers in a material. By applying a known magnetic field perpendicular to the current flow and measuring the resulting Hall voltage, the mobility of the charge carriers can be calculated using the formula:

\[ \mu = \frac{V_H}{B \cdot I \cdot d} \]

where:
- \(\mu\) is the mobility of the charge carriers
- \(V_H\) is the Hall voltage
- \(B\) is the magnetic field strength
- \(I\) is the current flowing through the material
- \(d\) is the thickness of the material

Carrier concentration:
The Hall effect can also be used to determine the carrier concentration in a material. By measuring the Hall voltage and knowing the values of the magnetic field strength, current, and material dimensions, the carrier concentration can be calculated using the formula:

\[ n = \frac{1}{e \cdot R_H} \]

where:
- \(n\) is the carrier concentration
- \(e\) is the elementary charge
- \(R_H\) is the Hall coefficient

Type of semiconductor (p or n):
The Hall effect can also be used to determine the type of semiconductor, whether it is p-type or n-type. The sign of the Hall voltage indicates the majority carrier type. If the Hall voltage is positive, it indicates that the majority carriers are holes, corresponding to p-type material. If the Hall voltage is negative, it indicates that the majority carriers are electrons, corresponding to n-type material.

Diffusion constant:
The diffusion constant is a measure of how particles or charge carriers spread out in a material due to diffusion. It is a property related to the movement of particles and their random motion, rather than their interaction with a magnetic field. Therefore, it cannot be determined using the Hall effect, which relies on the interaction between charge carriers and a magnetic field.

Conclusion:
In conclusion, the Hall effect can be used to measure the mobility of charge carriers, carrier concentration, and type of semiconductor (p or n). However, it cannot be used to determine the diffusion constant, as this property is related to the random motion of particles rather than their interaction with a magnetic field.