launch file error: Invalid roslaunch XML syntax

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I've written this code with 2 other similar ones, but only this code is giving me the error.

<launch>
<node pkg="diff_drive" type="diff_drive_controller" name="diff_drive_control">
<param name="~ticks_per_meter" value="8000"/>
<param name="~wheel_seperation" value="10"/>
<param name="~max_motor_speed" value="10"/>
<param name="~timeout" value= "2"/>

<node pkg="rqt_graph" type="rqt_graph" name="rqt_graph"/>
</launch>

And this is the error:

RLException: Invalid roslaunch XML syntax: mismatched tag: line 9, column 2.
The traceback for the exception was written to the log file