Nitrogen dioxide is one of the many oxides of nitrogen (often collectively called "NOx") that are of interest to atmospheric chemistry. It can react with itself to form another form of NOx, dinitrogen tetroxide.

A chemical engineer studying this reaction fills a 75L tank with 23. mol of nitrogen dioxide gas. When the mixture has come to equilibrium he determines that it contains 17.7 mol of nitrogen dioxide gas. The engineer then adds another 5.8mol of nitrogen dioxide, and allows the mixture to come to equilibrium again. Calculate the moles of dinitrogen tetroxide after equilibrium is reached the second time. Round your answer to 2 significant digits.