Kim Little continued her phenomenal scoring run with two first-half goals to take her season's tally to 39.
It would have been even better for the Scotland star if she had not missed a penalty between her 11th and 29th-minute strikes.
Ciara Grant added the third goal seven minutes into the second period, but three minutes later an Emma Beckett penalty reduced the arrears.
An Arsenal victory was never in doubt, however, and the three points were assured by goals from Rachel Yankey and Helen Lander in the final 12 minutes.
The result kept the Gunners one point behind Leeds to set up what should be the Premier League's match of the season when the two sides clash on Sunday.
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