  X-ray observations of galaxy clusters potentially provide powerful
cosmological probes if systematics due to our incomplete knowledge of the
intracluster medium (ICM) physics are understood and controlled. In this paper,
we present mock Chandra analyses of cosmological cluster simulations and assess
X-ray measurements of galaxy cluster properties using a model and procedure
essentially identical to that used in real data analysis. We show that
reconstruction of three-dimensional ICM density and temperature profiles is
excellent for relaxed clusters, but still reasonably accurate for unrelaxed
systems. The total ICM mass is measured quite accurately (<6%) in all clusters,
while the hydrostatic estimate of the gravitationally bound mass is biased low
by about 5%-20% through the virial region, primarily due to additional pressure
support provided by subsonic bulk motions in the ICM, ubiquitous in our
simulations even in relaxed systems. Gas fraction determinations are therefore
biased high; the bias increases toward cluster outskirts and depends
sensitively on its dynamical state, but we do not observe significant trends of
the bias with cluster mass or redshift. We also find that different average ICM
temperatures, such as the X-ray spectroscopic Tspec and gas-mass-weighted Tmg,
are related to each other by a constant factor with a relatively small
object-to-object scatter and no systematic trend with mass, redshift or the
dynamical state of clusters. We briefly discuss direct applications of our
results for different cluster-based cosmological tests.
