The Solid State

Step 1: Understanding coagulation power.
Coagulation power refers to the ability of an electrolyte to cause the aggregation or clumping of colloidal particles. The coagulation power increases with the valency of the ions and the charge they carry. Step 2: Comparing the electrolytes.
- provides Na+ ions, which are monovalent. - provides Ba2+ ions, which are divalent. - provides Al3+ ions, which are trivalent. Since the coagulation power increases with the charge of the ion, AlCl3 has the highest coagulation power, followed by BaCl2, and finally NaCl. Step 3: Conclusion.
The correct order of coagulation power is (4) AlCl3 \textgreater BaCl2 \textgreater NaCl.

Step 1: Understanding adsorption theory.
The adsorption theory explains the process where reactant molecules are adsorbed on the surface of a solid catalyst. This theory is primarily applicable in heterogeneous catalysis, where the catalyst is in a different phase from the reactants.
Step 2: Analyzing the options.
(1) Homogeneous catalysis: This involves catalysts and reactants in the same phase and does not follow the adsorption theory.
(2) Heterogeneous catalysis: The adsorption theory is specifically applicable here, as the catalyst is in a different phase (usually solid) and the reactants are adsorbed onto its surface.
(3) Auto catalysis: This is when a product of the reaction catalyzes its own formation. Adsorption theory does not apply in this case.
(4) Induced catalysis: This involves a catalyst being activated by the reactants, not necessarily involving adsorption.
Step 3: Conclusion.
The correct answer is (2) Heterogeneous catalysis.

Step 1: Formula for density.
Density ( ) is given by the formula: where: - is the number of atoms per unit cell (for face-centered cubic, ), - is the molar mass of gold (197 g/mol), - is Avogadro's number ( ), - is the unit cell length (4.07 Å = m). Step 2: Substituting the values.
Substitute the values into the density formula: Step 3: Conclusion.
The correct density of gold is . The correct answer is (1) 19.32 g.