How many formula units of sodium nitrate will react with 20.0 g of calcium carbonate to product sodium carbonate and calcium nitrate according to the following reaction? 2 Na(NO3) + Ca(CO3) Na2(CO3) + Ca(NO3)2

Sound travels about 750 miles per hour. a) suppose it takes about 1.5 seconds to hear the echo. how far away is the canyon wall, in feet? for this i got 825 ft b) suppose you stand 1,925 feet from the canyon wall and sound the horn. how long will it take to hear the echo? (i'm stuck on this)