he fifth and easily the best game so far in the world chess championship match was adjourned yesterday with challenger Victor Korchnoi pushing for a win and champion Anatoly Karpov struggling to hold for a draw. Karpov, playing black sealed his 42nd move in a large, white envelope which will be opened when play resumes today. He was facing a variety of threats, including the almost certain loss of a pawn and a difficult end-game.

Argentine grandmaster Miguel Najdorf commented that "Korchnoi has a very good chance for a win," and American grandmaster Robert Byrne agreed: "Korchnoi has winning chances."

Non-chess highlights of the day included a tropical storm and the final solution of the yogurt problem.Korchnoi let the deadline pass without protesting the yogurt decision, so until further notice Karpov may have yogurt delivered to him at the table at prearranged times. Because of the suggestion that the yogurt may have a code meaning, it was specified that the champion must eat blueberry yogurt unless he receives permission to change the flavor.

The tropical storm made a loud noise on the roof of the hall and cause a brief power failure while Karpov was deliberating his 23rd move - at approximately the same time that the champion's power was failing on the board.

Korchnoi held and pressed the initiative through most of the game, and some of Karpov's moves, which seem freely chosen at first glance, were virtually forced. On his 22nd, for example, the champion might have prefered 22 . . . N-B4, intensifying the attack on white's isolated QP, but instead he had to play 22 . . . N-Q4 to avoid serious loss (for example, 22 . . . N-B4; 23. BxP, PxB; 24. NxPch, winning the queen).

In the final position, black has to guard against at least two significant threats which are hard to parry simultaneously: the capture of his KBP and the exchange of the white KB for the black rook.

For example: 42 . . . Q-B2 allows an immediate 43. QxP. One alternative, 42 . . . N-K2, defends the pawn temporarily but leads to greater complications - for example: 43. B-R4, Q-B2; 44. R-K1; 45. BxN, RxB; 46. RxR, QxP, and white has an extra pawn and a paralyzing grip on the position.

Either 2 . . . N-R2 or 42 . . . R-BI allows white to capture the KBP after 43. B-K5. Finally, 42 . . . R-K1; 43. B-K5 pushes black toward a risky exchange of rook for bishop.