A particular form of cinnabar (HgS) adopts the zinc blende structure. The length of the unit cell edge is \(5.852 \AA\).
(a) Calculate the density of HgS in this form.
(b) The mineral tiemannite (HgSe) also forms a solid phase with the zinc blende structure. The length of the unit cell edge in this mineral is \(6.085 \AA\). What accounts for the larger unit cell length in tiemmanite?
(c) Which of the two substances has the higher density? How do you account for the difference in densities?
Text Transcription:
5.852 \AA
6.085 \AA
Step 1 of 5) Water ionizes to a slight degree, forming. The extent of this autoionization is expressed by the ion-product constant for water:. This relationship holds for both pure water and aqueous solutions. The Kw expression indicates that the product of 3H+4 and 3OH-4 is a constant. Thus, it decreases. Acidic solutions are those that contain more H+1aq2 than OH-1aq2, whereas basic solutions contain more OH-1aq2 than H+1aq2. When 3H+4 = 3OH-4, the solution is neutral. The concentration of H+1aq2 can be expressed in terms of the pH of a neutral solution is 7.00, whereas the pH of an acidic solution is below 7.00, and the pH of a basic solution is above 7.00. This p notation is also used to represent the negative logarithm of other small quantities, as in pOH and pKw. The pH of a solution can be measured using a pH meter, or it can be estimated using acid–base indicators.
