The much-changed visitors created the first opening in the 15th minute when 19-year-old Emile Smith Rowe saw his shot saved by Amaud Bodart while, just past the half-hour mark, Bukayo Saka’s effort from a tight angle was kept out by the goalkeeper’s legs.
Saka was Arsenal’s best player in the first half and he went close again only to see his left-footed strike fly over the bar.
The Gunners were the better team in the first period and Bodart had to be alert again in stoppage time to keep another Saka effort out before saving a glancing header from Reiss Nelson.
However, the Belgian side improved in the second half and they broke the deadlock against the run of play three minutes after the interval when Samuel Bastien’s shot was deflected past the wrong-footed Emiliano Martinez in the Arsenal goal.
Standard added a second goal in the 70th minute when a dreadful Joe Willock clearance was latched on to by Selim Amallah whose shot took a deflection off Konstantinos Mavropanos on its way past the hapless Martinez.
Arsenal appeared to be heading to defeat but, in the 78th minute, Alexandre Lacazette pulled a goal back before Saka grabbed the equaliser two minutes later with a sublime curling effort.
The Gunners will now turn their attention back to the Premier League and the visit of Manchester City to the capital on Sunday