Sandstones differs greatly in density depending on it's porosity and moisture content, so it is difficult to make a blanket statement about it's weight. It ranges from about 110 to 160 lbs/ft3.
That depends on what's in the cubic foot.If it's air, then it weighs only a fraction of a single pound.If it's water, then it weighs about 62 pounds.If it's stones or gold, then it weighs several...