Can the US be trusted? Can Russia be trusted? Neither can be trusted, they both simply say what the public want to hear while keeping secrets from it's population, everyone's attention is focused on Russia because of the media but US isn't any better really so Russia leis so that US can lie after that, lets all enjoy the lies!
Who in their right minds will believe that Russia will destroy a single chemical weapon, let alone all of them? Russia is just saying what the world wants to hear. There is no way to verify if they are even going to shut down a chemical weapons plant so they are just going to keep all of the weapons.
Russia recently demonstrated that it is developing a nuclear weapon capable of wiping out the entire state of Texas with a single strike. The weapon is 1,000 times more powerful than the bombs dropped on Hiroshima and Nagasaki. Russia will continue to develop chemical and all manner of other weapons if they feel it is in their interest.
Russia has made many claims before that they have not followed through with. Not only that but they recently decided to reinstate the KGB. It would be nice if they were being honest and they really followed through with this, but their is little chance of it happening in the near future.
President Putin's actions over the past couple of months have made it clear that he is a belligerent president and would not step back from major confrontations with NATO nations. In addition to this, the actions of his military in Syria have shown that he does not care about civilian casualties. Therefore it very unlikely that he cares enough about the ethical implications of using chemical weapons to destroy Russia's stockpile.