How many moles in 2.5 x 10^24 atoms of calcium

Which formula equation represents the burning of sulfur to produce sulfur dioxide? s(s) + o2(g) 4502(9) 2h2s(s) + 302(g) —> 2h20(0) + 2502(9) 4fes2+1102 —> 2fe2o3 + 8502 2802(g) + o2(9) v205 , 2503(9)

An object of mass 10.0 kg and volume 1000 ml and density 10 g/ml sinks in water who’s density is 1.0 g/ml. what is the mass of the water which has been displaced in kilograms

Asolution of naoh has a concentration of 25.00% by mass. what mass of naoh is present in 0.250 g of this solution? use the periodic table in the toolbar if needed. 0.0625 g what mass of naoh must be added to the solution to increase the concentration to 30.00% by mass? g