Question about some moves of last night's game

15Qa3 Qxa3

why anand choose to exchange queen with topalov while he have many other good moves to do?

29 Rb3 why he choose Rb3 instead of Rb7?

what's the advantage of that Rb3 move?

31 Rc5

Why doesn't anand choose Rc6 which is a white square so the bishop won't threaten the rook in the next move?

or making the bishop chasing his rook is all part of the plan?

15. Qa3 was one of the more important moves of the game- Anand appears to have liked taking the queens off the board and opening the queenside. I've seen it given !? because it is an intersting, game-changing move that ended up working out.

on 29. Rb3, white is defending against 29 ... Rxd3. If then (and white had moved to b7), 30. exd3 e2+ wins for black. 30. Rxa7 gets rid of that threat but also weakens white's position- the Knight is very good for him there and he wants to defend it.

On 31, White is plannening to take the a pawn, which he does on the next move. The threat by the bishop is no real problem.

also 25.....Ne3 someone said it was a blunder for topalov.

why?

didn't he exchange teh knight for a B?

I think the reason that 25 ... Ne3 was so bad was that it wasted a rather well positioned knight that was part of most of blacks chances for counterplay on an exchange that didn't achieve anything. It left white with a lot of spacial control of the queenside and an impenetrable position but didn't do much for black. It didn't lose material because it was an exchange, but it let white do as he pleased with the rest of the pieces.

Bishop for knight trades are seldom easy to evaluate. In this case, 25...Ne3 did two things wrong:

1. It closed off the e3-square and eliminated all possibility of a knight landing on c3

2. Black's knight was well-placed on d5; it shielded the h1-a8 diagonal and defended the precious b6-pawn. White's d2-bishop, on the other hand, wasn't doing much, besides guarding the outposts that the d5-knight wanted to occupy.

"25...Ne3? Now the real mistake comes. I think Topalov got tired of making moves without any idea. He wanted to force things. However there was another way... 25...Ng4! Fits perfectly with h5. "- GM Anish Giri from chessbase

so that''blunder'' is all about losing center control?

not really a blunder is just a small mistake but costly for black, btw a blunder is made with two '??' not one. 

then

29 Rb3 why he choose Rb3 instead of Rb7?

what's the advantage of that Rb3 move?

"....unable to win the pawn by force, but obviously he still has a big advantage. 29.Rb3! So that Topalov can forget about any Rxd3"-  GM Anish Giri

It seem to me it stop ...Rxd3 so later if d2 discover check ! and the d-pawn could be promoted to a queen

ok here what might happen if 29.Rb7 instead Rxd3 30.Rxa7 (not exd3 ? e2+ 31.Rxa7 e1=Q+ too good for black)  Rd2  31.Rcc7

o

so it means that R protect the important N? since the N get the center control?

Yes, I suppose you can say it that way :-)

also, 35 Nb4

i read many comments and said that this move is brilliant.

does this move make topalov to be in a passive way or what?

What about 35 ... Rxa3?!

Loses the exchange but gains a pawn.....

"The mean World Champion, who already gave the pawn once in the opening, doesn't want to give it now anymore. And he is right... this will be the decisive pawn! 34...Ra2?! (maybe too passive-kco)  34...Nd5 It was necessary to still try to complicate the matter a bit, but White is winning anyway. 35.Nb4! All suporters of Anand were now very relieved when they saw the black king standing on g8, not g7...( I don't understand this bit-kco)  35...Bxb4 [35...Rxa3 36.Rxa3 Bxb4 37.Ra8+! is what I meant with my previous comment.]"-  GM Anish Giri

dang it I am beginning to feel like I am BorgQueen answering to kurogkug's neverending questions !!  :-)

No offence fiveofswords but comments like this make you look like a bit of an arse. We lower rated players are told to study master games to get a better understanding of the game. It appears that's what the OP is doing.

Well, I bet this isn't the only thing he is doing to try and improve. Aslong as he is trying to improve, what harm will come from also looking at the World championship match?

Heck, looking at, and trying to understand a super-gm game (a great one aswell!) might not be the wast way to improve as a beginner, but it will definately enhance your love for the game.