Density of Silver:
The given information states that the density of silver is 10.5*10^3 kg/m^3. This means that for every cubic meter of silver, there is a mass of 10.5*10^3 kg.

Conducting Electrons:
In metallic substances like silver, the valence electrons are free to move throughout the entire material. These mobile electrons are responsible for the high electrical conductivity of metals.

It is assumed that each silver atom provides one conducting electron. This assumption is based on the fact that silver has one valence electron in its outermost energy level.

Conductivity of Silver:
The given information also states that the conductivity of silver at 20°C is 6.8*10^7 S/m. Conductivity is a measure of how well a material conducts electricity. It is the reciprocal of resistivity.

Calculating Density of Electrons:
To calculate the density of electrons, we need to know the atomic weight of silver. The atomic weight of silver is given as 107.9*10^-3 kg/mol.

To find the number of atoms in one mole of silver, we can use Avogadro's number, which is approximately 6.022*10^23 atoms/mol.

So, the mass of one mole of silver can be calculated as follows:

Mass of one mole of silver = Atomic weight of silver * Avogadro's number
= 107.9*10^-3 kg/mol * 6.022*10^23 atoms/mol
≈ 6.5 kg

The mass of one mole of silver is approximately 6.5 kg.

The density of electrons can be calculated by dividing the density of silver by the mass of one mole of silver:

Density of electrons = Density of silver / Mass of one mole of silver
= 10.5*10^3 kg/m^3 / 6.5 kg
≈ 1615*10^3 electrons/m^3

Therefore, the density of electrons in silver is approximately 1615*10^3 electrons/m^3.

Calculating Mobility of Electrons:
The mobility of electrons is a measure of how easily they can move through a material when subjected to an electric field. It is denoted by the symbol μ (mu).

The mobility of electrons can be calculated using the formula:

Mobility (μ) = Conductivity (σ) / Density of electrons (n)

Substituting the given values:

Mobility (μ) = 6.8*10^7 S/m / 1615*10^3 electrons/m^3
≈ 42100 m^2/(V*s)

Therefore, the mobility of electrons in silver with an atomic weight of 107.9*10^-3 kg/mol is approximately 42100 m^2/(V*s).

In summary, the density of electrons in silver is approximately 1615*10^3 electrons/m^3, and the mobility of electrons is approximately 42100 m^2/(V*s). These values are calculated based on the given density of silver, the assumption that each silver atom provides one conducting electron, and the conductivity of silver at 20°C.