Dani Olmo scored twice, and Raphinha also got on the scoresheet in an impressive first-half display from the league leader, who had the points virtually secured after just half an hour against their city neighbors.
Olmo put Barca ahead after 12 minutes following a spectacular pass from Lamine Yamal with the outside of his foot, reports Xinhua.
Raphinha doubled Barca's advantage 10 minutes later after Marc Casado produced a trademark defense-splitting pass for him to clip the ball over Espanyol goalkeeper Joan Garcia.
Olmo then scored the third goal after half an hour, drilling in a powerful shot close to the post after being given too much time outside the Espanyol area.
Barcelona eased off in the second half, and Javi Puado scored a consolation goal for Espanyol in the 63rd minute.
Atletico Madrid claimed a much-needed confidence boost with a 2-0 win at home to Las Palmas, ending a run of poor displays.
Giuliano Simeone gave his father Diego a helping hand by putting Atletico ahead in the 36th minute against a rival that had traveled to Madrid looking to defend a draw. Alexander Sorloth scored Atletico's second in the 83rd minute.
The game suffered a long stoppage in the second half after Las Palmas goalkeeper Jasper Cillessen had to be carried off following a collision with Atletico's Nahuel Molina.
Athletic Club and Betis drew 1-1 in a game the home side will wonder how they didn't win after hitting the woodwork three times in the first half.
Pablo Fornals put Betis ahead in the second half with their first shot of the game, but a header from Aitor Berenguer saved a point for Athletic, who would have gone on to win but for several excellent saves from Betis goalkeeper Rui Silva.
Real Sociedad won 2-0 away to Sevilla with a convincing display that saw Takefusa Kubo open the scoring with an excellent individual goal in the 34th minute.
Mikel Oyarzabal scored the second from the penalty spot with 20 minutes left to play after Martin Zubimendi was the victim of a straight-arm challenge inside the Sevilla penalty area.
On Saturday, Ante Budimir's 18th-minute penalty gave Osasuna a 1-0 win at home to struggling Valladolid in their El Sadar Stadium. Budimir hit the post in the second half as Osasuna dominated against a rival that has only eight points from its first 12 games and a dreadful goal difference of minus 15.
Injury-hit Girona won a thrilling game 4-3 at home to Leganes, although they had to dig deep as the visitors twice came back from a goal down.
Miguel Gutierrez opened the scoring for Girona, but Renato Tapia quickly pulled Leganes level minutes later.
Arnau Martinez responded to restore Girona's lead, before Juan Cruz made it 2-2 before halftime.
A penalty from substitute Cristhian Stuani and an own goal from Sergio Gonzalez looked to have won the game for Girona, but Munir El Haddadi's thunderbolt made it 4-3, giving Girona a nervous end to the game.
On Friday night, Alaves ended a five-game losing streak with a 1-0 win at home to Mallorca, with Jon Guridi netting the only goal of the match with 15 minutes left to play.
(IANS)
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