Hosts raced into four-goal advantage after 30 minutes
The guests would have wanted to make a positive start to the match, but instead the southerners endured a nightmare quarter of an hour that put the tie out of reach.
Lionel Messi, who had already planted a fine chance wide, opened the scoring after 10 minutes, though not in his usual graceful style. After driving past a couple of tame challenges around the edge of the box, the Argentine fired a rather tame shot that bobbled over Esteban and into the net.
The visiting custodian would again be partially culpable when Barca scored a second moments later. Xavi broke the midfield line of the visitors and burst positively forward, waiting until the time was right to release David Villa on the left. The ex-Valencia man stepped inside Michel Macedo before delivering a low shot into the net, though Esteban, having got a glove to the ball, perhaps should have made the stop.
Some brief resistance, led by Henok Goitom, was abruptly ended by Messi’s second of the evening. Again it was a quick counterattack that caught out the visitors, and on this occasion it was Andres Iniesta who provided the ammunition for the South American, who bent a cultured finish into the corner of the net from the right corner of the box. This strike was Barca’s 100th of the season.
Rampant, Pep Guardiola’s side found their fourth goal of the evening as the clock ticked round to the half-hour mark, and this one was to be something of a collectors’ item. From a free-kick, Xavi elected to play a high cross into the box, from which Pedro leaped highest to glance an unlikely but magnificent header into the top corner of the goal.
A couple of minutes from full-time, the home side struck a fifth. A superb lobbed pass from Messi picked out a terrific run from substitute Seydou Keita, whose first touch was accurate and his second deadly.
This proved the end of the scoring, but Barca might have had more goals. Villa had an effort correctly disallowed in the first half for offside, while Messi would have a brilliant dribble end with a fine low stop from Esteban.
After the break, the Argentine released a wonderful pass for the over-lapping Maxwell, though the left-back could only rattle the post from a difficult angle.
A superb flowing move from Barca ended with Adriano attempting to bend a shot into the top corner of the net only for Esteban to make a good stop, and soon afterwards the goalkeeper would be exerted once again, denying a fine effort from Javier Mascherano.
Opportunities for the guests were rare in the extreme, though Jose Pinto was called into evasive action just before the break, when he reached towards his top right corner to push away an Albert Crusat half volley.
Out of the blue, Goitom found himself through on Pinto with 25 minutes remaining, but his finish lacked conviction, with the ball dribbling tamely wide.
Full value for their 5-0 victory, it seems that Barcelona will have a routine time in the second leg in Almeria next week, though Guardiola will be hoping to avoid the kind of defeat handed to them by Betis after they had won their quarter-final first leg by an identical score.
In tonight's other semi-final first leg, Real Madrid won 1-0 at Sevilla, putting Spain's two giant clubs on course to meet in the final.