Thanks to his pressure against f7 and active rook on e8, White clearly stands better. Play continued 31...Qc7 32.Qe4 Qc3 33.Ba4 Rc7 34.Bf4! Rc4 35.Qe3 Qa1+ (35...Bxf4? loses to 36.Rxf8+ Kxf8 37.Qe8 mate) 36.Kg2 Qf6 37.Bg5 Qf5 38.Bb3 Rc8 39.Rxc8 Qxc8 40.Qxa7.
White's manoeuvring has finally borne fruit. His extra pawn should now be enough to win. There followed 41...Ne6 42.Bd2 Be5 43.Bxe6 fxe6 44.Qc5 Qe4 45.Be3 Bb2 46.a4 Kh7.
White has problems exploiting his advantage because of the good position of the black queen. His next two moves, however, make matters more difficult.
47.h3 e5 48.Kh2 Ba3 49.Bd2 Bb2.
Now 50.Qe3 must be the correct move, though after 50...Qc4 the threat of Bd4 makes it difficult for White to make progress. The move White played instead was either a huge miscalculation or an oversight.
50.Bc3 b6! 51.Qxe5 (What else? 51.Qc7 is met by 51...Qc2) 51...Qxe5 52.Bxe5 Bxe5 53.a5 b5! 54.Kg2 Kg8 55.f4 Bb8 56.Kf3 Kf7 57.Ke4 Ke6 58.g4 Kd6 59.h4 Kc6 60.a6 Bd6 61.a7 Kb7 and White resigned. Black will capture the pawn on b4, with an easy win.
After he had lost such an endgame after being a clear pawn ahead, one can understand why Arencibia lost confidence and made some uncharacteristically bad moves later in the event. As White against Alex Yermolinsky, he opened 1.d4 Nf6 2.Nf3 g6 3.c4 Bg7 4.Nc3 0-0 5.e4 d6 6.Be2 e5 7.0-0 exd4 8.Nxd4 Re8 9.f3 c6 10.Be3 d5 11.cxd5 Nxd5! 12.Bf2 Nf4. By allowing 10...d5, White has given his opponent an easy game. 11...Qg5 is an irritating threat, but after 12.Kh1 there is nothing wrong with White's position. Instead, he played 12.h4? which should have been rejected on grounds of ugliness if nothing else. In fact, after Black's reply of 12...Bh3! White was already lost since 13.gxh3 Nxh3+ will be followed by Nxf2 and loss of the knight on d4.
Finally, here is Arencibia's loss to Ivanchuk. White's opening play with 7.Qd3 and 10.Qh3 was unusual, but not quite as bad as it was made to look in this game. Black's 12...Rxc3 is a standard sacrifice in such positions, but 14.e5 would have been a more testing continuation that White's Bxf6, after which he could offer no real defence to the attack on his king.
White: W Arencibia
Black: V Ivanchuk
1 e4 c5 12 0-0-0 Rxc3
2 Nf3 d6 13 bxc3 Nc5
3 d4 cxd4 14 Bxf6 Bxf6
4 Nxd4 Nf6 15 Rhe1 Qa5
5 Nc3 a6 16 e5 dxe5
6 Bg5 e6 17 fxe5 Bg5+
7 Qd3 b5 18 Kb1 Bd5
8 a3 Nbd7 19 Nb3 Qxa3
9 f4 Bb7 20 Bxb5+ axb5
10 Qh3 Be7 21 Rxd5 Na4
11 Bd3 Rc8 White resigns