Mercury melts at 234.3 k. convert this this melting point to degrees celcius

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

Solutions of sodium carbonate and silver nitrate react to form solid silver carbonate and a solution of sodium nitrate. a solution containing 3.50 g of sodium carbonate is mixed with one containing 5.00 g of silver nitrate. how many grams of sodium carbonate, silver nitrate, silver carbonate, and sodium nitrate are present after the reaction is complete?

How many moles of oxygens atoms are present in 5.00 mol of diphosphorus of fe2(so4)3