"Oh there I am!" squealed an ebullient Joan Mondale, stopping at the entrance of the National Gallery's Center for Advanced Studies to enjoy a much enlarged photograph of herself explaining a National Gallery masterpiece to a group of schoolchildren.

When Gallery director J. Carter Brown turned up at her elbow to greet her, she effervesced again: "I just saw my picture of myself. That's why everyone recognizes me!"

While throngs mobbed the adjoining East Building to glimpse Chinese Vice Premier Tent Hsiao-ping at a separate reception, Mondale made her way up the elevator to the seventh floor of the not-yet-finished Center for Advanced Studies to deliver an after-dinner talk entitled "The Future Art."

Her audience included 100 members of the Congressional Clearinghouse on the Future, an ad hoc caucus that provides information to Congress on various asspects of the future.

She plunged into the pre-dinner throng, which included one freshman senator, William Thad Cochran (R) of Mississippi and dozens of members of Congress, among them Lindy Boggs (D-La.), Bill Lehman (D-Fla.), Berkely Bedell (D-Iowa), Rovert Edgar (D-Pa.), Timothy Wirth (D-Colo.) and Father Rovert Drinan (D-Mass.), who delivered the invocation, asking for blessings, upon Mondale and upon the future before sitting down to a dinner of tenderloin of beef, haut-Medoc and key lime mousse.

During the meal, the legislators and futurists frequently invoked the names of Buck Rogers, Jules Verne and George Orwell as artists who had been harbingers of future events.

"We believe that art tells us a lot about the future, if we can just see it," said Clearinghouse trends administrator Lena Lupica, explaining why the Clearinghouse had launched this year's monthly "Chautauquas for Congress" with a series of talks and films on the subject: "What do artists tell us about future?"

Mondale alternately had her listeners rolling in the aisles and rising to their feet in applause as she reiterated a basic theme: "Art is not a mere frill, like a gilded bathtub faucet," and went on to point out that "the arts are both booming and begging, rising and threatened."

She added that although the National Endowment for the Arts has districuted $600 million since it began in 1965, that more funding would have to come from "newer, smaller local and regional foundations that can take chances. I can see a new regional consciousness emerging.

"But we must now have increased interest in the probblems of the individual artist. We have been preoccupied with getting out cultural institutions on their feet, but it is the individual artist who forms the foundation on which the art institutions are built."

In a brief question period after the talk, a woman from Buffalo asked, "How do you get a positive attitude toward the arts going where there isn't one?"

"Just keep talking," said Mondale.