What will happened to the rock cycle without erosion

What does x represent in the formula for the compound xcl4?

The human eye contains a molecule called 11-cis-retinal that changes shape when struck with light of sufficient energy. the change in shape triggers a series of events that results in an electrical signal being sent to the brain that results in vision. the minimum energy required to change the conformation of 11-cis-retinal within the eye is about 164 kj/mol.

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?