Barcelona were better than Arsenal in the first leg: they had some troubles, but in general that win was confident. These teams play in different weight classes, so there are no chances for Arsenal to qualify.
Barcelona can surely win the upcoming game. The Catalans have no need to save pains because they are comfortably leading in La Liga. And all of the experienced Barca players understand that they shouldn’t underestimate the opponent. So Barcelona have enough motivation to defeat Arsenal.
But I also expect Arsenal to score here. They can’t stay goalless in two games in a row even against Barcelona. If the Catalans score one or two, Arsenal will still have some chances to score a consolation goal.