Answer
$SO_3(g)+H_2O(l)\rightarrow H_2SO_4(aq)$
Work Step by Step
Sulfur trioxide is $SO_3$, water is $H_2O$, sulfuric acid is $H_2SO_4$.
$SO_3(g)+H_2O(l)\rightarrow H_2SO_4(aq)$
The equation is in balance with no adjustments.
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