Iron oxide (feo) has the rock salt crystal structure and a density of 5.70 g/cm3. the atomic weights of iron and oxygen are 55.85 g/mol and 16.00 g/mol, respectively. (a) determine the unit cell edge length

The unit cell edge length is  

Explanation:

NaCl has FCC structure. and so is the FeO.

Number of atom in unit cell of FCC (Z) = 4

Density of FeO=

Edge length = a

Atomic mass of FeO(M) = 55.85 g/mol +16.00 g/mol = 71.85 g/mol

Formula used :  

where,

= density

Z = number of atom in unit cell

M = atomic mass

= Avogadro's number  

a = edge length of unit cell

On substituting all the given values , we will get the value of 'a'.

The unit cell edge length is  

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."