The al2o3 crystal structure (corundum) consists of an hcp arrangement of o2- ions; the al3+ ions occupy octahedral positions. what fraction of the available octahedral positions are filled with al3+ ions? in corundum, the al3+ ions do not fill the tetrahedral positions.

The fraction of the available octahedral positions are filled with ions is

Explanation:

If there are n numbers of spheres in HCP in packing:

Number of octahedral void = n

Number of tetrahedral void = 2n

Total number of voids = n + 2n = 3n

The crystal structure consists of an HCP arrangement of ions.

Number of spheres in HCP = 6

Number of = 6

Number of octahedral voids = 6

Number of tetrahedral void = 12

Number of aluminum ions when there are 6 ion =

Number of voids in which ions are present = 4

The fraction of the available octahedral positions are filled with ions =

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol